Document:

Exhibit 10.6

STOCK ESCROW AGREEMENT

 

This STOCK ESCROW AGREEMENT,
dated as of [●], 2021 (“Agreement”), by and among MOUNT RAINIER ACQUISITION CORP., a Delaware corporation (“Company”)
and the initial stockholders listed on the signature pages hereto (collectively, the “Initial Stockholders”) and AMERICAN
STOCK TRANSFER & TRUST COMPANY, LLC, a New York limited liability trust company (“Escrow Agent”).

 

WHEREAS, the Company has entered
into an Underwriting Agreement, dated as of [●], 2021 (“Underwriting Agreement”), with A.G.P./Alliance Global Partners,
as representative of the underwriters ( the “Underwriters”), pursuant to which, among other matters, the Underwriters have
agreed to purchase 15,000,000 units (“Units”) of the Company, plus an additional 2,250,000 Units if the Underwriters exercise
their over-allotment option in full. Each Unit consists of one share of common stock of the Company, par value $0.0001 per share (the
 “Common Stock”), and one warrant, with each warrant entitling the holder thereof to purchase three-fourths of one share of
the Common Stock at an exercise price of $11.50 per whole share, all as more fully described in the Company’s final Prospectus,
dated [●], 2021 (“Prospectus”), comprising part of the Company’s Registration Statement on Form S-1 (File No.
333-256816) under the Securities Act of 1933, as amended (“Registration Statement”), declared effective on [●], 2021
(“Effective Date”).

 

WHEREAS, the Initial Stockholders
have agreed as a condition of the sale of the Units to deposit their “founder shares” (as defined in the Prospectus), as set
forth opposite their respective names on Exhibit A attached hereto (collectively “Escrow Shares”), in escrow as hereinafter
provided.

 

WHEREAS, the Company and the
Initial Stockholders desire that the Escrow Agent accept the Escrow Shares, in escrow, to be held and disbursed as hereinafter provided.

 

IT IS AGREED:

 

1. Appointment of Escrow
Agent. The Company and the Initial Stockholders hereby appoint the Escrow Agent to act in accordance with and subject to the terms
of this Agreement and the Escrow Agent hereby accepts such appointment and agrees to act in accordance with and subject to such terms.

 

2. Deposit of Escrow Shares.
On or prior to the date hereof, each of the Initial Stockholders delivered to the Escrow Agent certificates representing such Initial
Stockholder’s respective Escrow Shares, together with applicable share powers, to be held and disbursed subject to the terms and
conditions of this Agreement. Each of the Initial Stockholders acknowledges that the certificate representing such Initial Stockholder’s
Escrow Shares is legended to reflect the deposit of such Escrow Shares under this Agreement.

 

3. Disbursement of the
Escrow Shares.

 

3.1 The Escrow Agent shall
hold the Escrow Shares during the period (the “Escrow Period”) commencing on the date hereof ending on the earlier of
(i) one year after the date of the consummation of the Company’s initial business combination (as described in the
Registration Statement, hereinafter a “Business Combination”) and (ii) the date on which the closing price of the Common
Stock equals or exceeds $12.00 per share (as adjusted for stock splits, stock dividends, stock capitalizations, reorganizations and
recapitalizations) for any 20 trading days within any 30-trading day period commencing at least 150 following the closing of the
Company’s initial Business Combination. The Company shall promptly provide notice of the consummation of a Business
Combination to the Escrow Agent. Upon completion of the Escrow Period, the Escrow Agent shall disburse such amount of each Initial
Stockholder’s Escrow Shares (and any applicable share power) to such Initial Stockholder; provided, however, that if the
Escrow Agent is notified by the Company pursuant to Section 6.7 hereof that the Company is being liquidated at any time during the
Escrow Period, then the Escrow Agent shall promptly destroy the certificates representing the Escrow Shares; provided further,
however, that if, after the Company consummates an initial Business Combination, the Company (or the surviving entity) subsequently
consummates a liquidation, merger, stock exchange or other similar transaction which results in all of the stockholders of such
entity having the right to exchange their shares of Common Stock for cash, securities or other property, then the Escrow Agent will,
upon receipt of a notice executed by the Chairman of the Board, Chief Executive Officer or other authorized officer of the Company,
in form reasonably acceptable to the Escrow Agent, certifying that such transaction is then being consummated or such conditions
have been achieved, as applicable, release the Escrow Shares to the Initial Stockholders. The Escrow Agent shall have no further
duties hereunder after the disbursement or destruction of the Escrow Shares in accordance with this Section 3.1.

 

     

     

    

 

3.2 Notwithstanding
Section 3.1, if the Underwriters do not exercise their over-allotment option to purchase an additional 2,250,000
Units of the Company in full within 45 days of the date of the Prospectus (as described in the Underwriting Agreement), the Initial
Stockholders agree that the Escrow Agent shall return to the Company for cancellation, at no cost, the number of Escrow Shares held
by the Initial Stockholders listed on Exhibit B determined by multiplying (a) the product of (i) 562,500
multiplied by (ii) a fraction, (x) the numerator of which is the number of Escrow Shares held by each such holder, and (y) the
denominator of which is the total number of Escrow Shares, by (b) a fraction, (i) the numerator of which is 2,250,000
minus the number of Units purchased by the Underwriters upon the exercise of their over-allotment option, and (ii) the denominator
of which is 2,250,000, without taking into account the transfer of the 300,000 representative shares (345,000 shares if the over-allotment option is exercised
in full) from A.G.P./Alliance Global Partners to the sponsor that took place on September 27, 2021. The Company shall promptly provide notice to the
Escrow Agent of the expiration or termination of the Underwriters’ over-allotment option and the number of Units, if any,
purchased by the Underwriters in connection with their exercise thereof.

 

4. Rights of Initial Stockholders
in Escrow Shares.

 

4.1 Voting Rights as a Stockholder.
Subject to the terms of the Insider Letters (as defined below) described in Section 4.4 hereof and except as herein provided, the Initial
Stockholders shall retain all of their rights as stockholders of the Company during the Escrow Period, including, without limitation,
the right to vote such shares.

 

4.2 Dividends and Other Distributions
in Respect of the Escrow Shares. During the Escrow Period, all dividends payable in cash with respect to the Escrow Shares shall be
paid to the Initial Stockholders, but all dividends payable in stock or other non-cash property (“Non-Cash Dividends”) shall
be delivered to the Escrow Agent to hold in accordance with the terms hereof. As used herein, the term “Escrow Shares” shall
be deemed to include the Non-Cash Dividends distributed thereon, if any.

 

4.3 Restrictions on Transfer.
During the Escrow Period, the only permitted transfers of the Escrow Shares will be (1) to any persons or entities (including their affiliates
and stockholders) participating in the private placement of the “private warrants” (as defined in the Prospectus), and officers,
directors, stockholders, employees and members of the Initial Stockholders and their respective affiliates, (2) amongst the Initial Stockholders
(including, to the extent the Initial Stockholders are entities, to such entity’s members, partners, stockholders or other equity
holders) or to the Company’s officers, directors and employees, (3) if any Initial Stockholder is an entity, as a distribution to
its partners, stockholders, or members upon its liquidation, (4) by bona fide gift to a member of the Initial Stockholder’s (or
its permitted transferee’s) immediate family or to a trust, the beneficiary of which is the Initial Stockholder (or its permitted
transferee) or a member of the Initial Stockholder’s (or its permitted transferee’s) immediate family, for estate planning
purposes, (5) by virtue of the laws of descent and distribution upon death, (6) pursuant to a qualified domestic relations order, (7)
by certain pledges to secure obligations incurred in connection with purchases of the Company’s securities, (8) by private sales
at prices no greater than the price at which the founder shares were originally purchased or (9) for the cancellation of up to 562,500
shares of Common Stock subject to forfeiture to the extent that the Underwriters’ over-allotment is not exercised in full or in
part or in connection with the consummation of the Company’s initial business combination, in each case (except for clause 9 or
with the Company’s prior consent) where such permitted transferee agrees to the terms of this Agreement and the Insider Letter (as
defined below).

 

4.4 Insider Letters.
Each of the Initial Stockholders has executed a letter agreement with the Representatives and the Company, dated as indicated on Exhibit
C hereto, and the form of which is filed as an exhibit to the Registration Statement (“Insider Letter”), respecting the
rights and obligations of such Initial Stockholder in certain events, including but not limited to the liquidation of the Company.

 

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5. Concerning the Escrow
Agent.

 

5.1 Good Faith Reliance.
The Escrow Agent shall not be liable for any action taken or omitted by it in good faith and in the exercise of its own best judgment,
and may rely conclusively and shall be protected in acting upon any order, notice, demand, certificate, opinion or advice of counsel (including
counsel chosen by the Escrow Agent), statement, instrument, report or other paper or document (not only as to its due execution and the
validity and effectiveness of its provisions, but also as to the truth and acceptability of any information therein contained) which is
believed by the Escrow Agent to be genuine and to be signed or presented by the proper person or persons. The Escrow Agent shall not be
bound by any notice or demand, or any waiver, modification, termination or rescission of this Agreement unless evidenced by a writing
delivered to the Escrow Agent signed by the proper party or parties and, if the duties or rights of the Escrow Agent are affected, unless
it shall have given its prior written consent thereto.

 

5.2 Indemnification.
The Escrow Agent shall be indemnified and held harmless by the Company from and against any expenses, including reasonable counsel
fees and disbursements, or loss suffered by the Escrow Agent in connection with any action, suit or other proceeding involving any
claim which in any way, directly or indirectly, arises out of or relates to this Agreement, the services of the Escrow Agent
hereunder, or the Escrow Shares held by it hereunder, other than expenses or losses arising from the gross negligence or willful
misconduct of the Escrow Agent (as determined by a court of competent jurisdiction in a final and non-appealable decision). Promptly after the receipt by the Escrow Agent of notice of any demand or claim or the commencement
of any action, suit or proceeding, the Escrow Agent shall notify the other parties hereto in writing. In the event of the receipt of
such notice, the Escrow Agent, in its sole discretion, may commence an action in the nature of interpleader in an appropriate court
to determine ownership or disposition of the Escrow Shares or it may deposit the Escrow Shares with the clerk of any appropriate
court or it may retain the Escrow Shares pending receipt of a final, non-appealable order of a court having jurisdiction over all of
the parties hereto directing to whom and under what circumstances the Escrow Shares are to be disbursed and delivered. The
provisions of this Section 5.2 shall survive in the event the Escrow Agent resigns or is discharged pursuant to Sections 5.5 or 5.6
below.

 

5.3 Compensation. The
Escrow Agent shall be entitled to reasonable compensation from the Company for all services rendered by it hereunder. The Escrow Agent
shall also be entitled to reimbursement from the Company for all expenses paid or incurred by it in the administration of its duties hereunder
including, but not limited to, all counsel, advisors’ and agents’ fees and disbursements and all taxes or other governmental
charges.

 

5.4 Further Assurances.
From time to time on and after the date hereof, the Company and the Initial Stockholders shall deliver or cause to be delivered to the
Escrow Agent such further documents and instruments and shall do or cause to be done such further acts as the Escrow Agent shall reasonably
request to carry out more effectively the provisions and purposes of this Agreement, to evidence compliance herewith or to assure itself
that it is protected in acting hereunder.

 

5.5 Resignation. The
Escrow Agent may resign at any time and be discharged from its duties as escrow agent hereunder by its giving the other parties hereto
written notice and such resignation shall become effective as hereinafter provided. Such resignation shall become effective at such time
that the Escrow Agent shall turn over to a successor escrow agent appointed by the Company, the Escrow Shares held hereunder. If no new
escrow agent is so appointed within the 90 day period following the giving of such notice of resignation, the Escrow Agent may deposit
the Escrow Shares with any court it reasonably deems appropriate.

 

5.6 Discharge of Escrow Agent.
The Escrow Agent shall resign and be discharged from its duties as escrow agent hereunder if so requested in writing at any time by the
other parties hereto, jointly, provided, however, that such resignation shall become effective only upon acceptance of appointment by
a successor escrow agent as provided in Section 5.5.

 

5.7 Liability. Notwithstanding
anything herein to the contrary, the Escrow Agent shall not be relieved from liability hereunder for its own gross negligence or its own
willful misconduct (as determined by a court of competent jurisdiction in a final and non-appealable decision). 

 

5.8 Waiver. The
Escrow Agent hereby waives any right of set-off or any other right, title, interest or claim of any kind (“Claim”) in,
or to any distribution of, the Trust Account (as defined in that certain Investment Management Trust Agreement, dated as of the date
hereof, by and between the Company and the Escrow Agent as trustee thereunder) and hereby agrees not to seek recourse,
reimbursement, payment or satisfaction for any Claim against the Trust Account for any reason whatsoever.

 

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6. Miscellaneous.

 

6.1 Governing Law. This
Agreement shall for all purposes be deemed to be made under and shall be construed in accordance with the laws of the State of New York,
without giving effect to conflicts of law principles that would result in the application of the substantive laws of another jurisdiction.

 

6.2 Third Party Beneficiaries.
Each of the Initial Stockholders hereby acknowledges that each of the Representatives is a third party beneficiary of this Agreement and
this Agreement may not be modified or changed without the prior written consent of the Representatives.

 

6.3 Entire Agreement.
This Agreement contains the entire agreement of the parties hereto with respect to the subject matter hereof and, except as expressly
provided herein, may not be changed or modified except by an instrument in writing signed by the party to the charged.

 

6.4 Headings. The headings
contained in this Agreement are for reference purposes only and shall not affect in any way the meaning or interpretation thereof.

 

6.5 Binding Effect. This
Agreement shall be binding upon and inure to the benefit of the respective parties hereto and their legal representatives, successors
and assigns; provided, that the Escrow Agent may not assign this Agreement without the prior written consent of the Company.

 

6.6 Notices. Any notice
or other communication required or which may be given hereunder shall be in writing and either be delivered personally or be mailed, certified
or registered mail, or by private national courier service, return receipt requested, postage prepaid, or by e-mail as described below,
and shall be deemed given when so delivered personally or by e-mail or, if mailed or sent by private national courier service, two days
after the date of mailing or the date of delivery to the private national courier service, as follows:

 

If to the Company or a Stockholder,
to: 

 

Mount Rainier Acquisition Corp.

256 W. 38th Street, 15th Floor

New York, NY 10018

Attn: Matthew
Kearney

 

Copy (which copy
shall not constitute notice) to:

 

Loeb & Loeb LLP

345 Park Avenue

New York, New York 10154

Attn: Mitchell Nussbaum, Esq.

Email: 

 

and if to the Escrow Agent, to:

 

American Stock Transfer & Trust
Company, LLC

201 15th Avenue |

Brooklyn, NY 11219

		Attn:	

 

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A copy (which copy shall not constitute
notice) sent hereunder shall be sent to:

 

A.G.P./Alliance
Global Partners

590 Madison Avenue, 28th Floor 

New York, NY 10022

Attn: Thomas J. Higgins

Email: 

 

and:  Manatt,
Phelps & Phillips LLP

695 Town Center Drive, 14th Floor

Costa Mesa, California 92626

Attn: Thomas J. Poletti

Email: 

 

The parties hereto consent
to the delivery of notices or other communication by electronic transmission at the e-mail address set forth below the respective party’s
name in Section 6.6 hereto. To the extent that any notice given by means of electronic transmission is returned or undeliverable for any
reason, the foregoing consent shall be deemed to have been revoked until a new or corrected e-mail address has been provided, and such
attempted electronic notice shall be ineffective and deemed to not have been given. Each party agrees to promptly notify the other parties
of any change in its e-mail address, and that failure to do so shall not affect the foregoing. The parties may change the persons and
addresses to which the notices or other communications are to be sent by giving written notice to any such change in the manner provided
herein for giving notice.

 

6.7 Liquidation of the Company.
The Company shall give the Escrow Agent written notification of the liquidation and dissolution of the Company in the event that the Company
fails to consummate a Business Combination within the time period specified in the Prospectus.

 

[Signature Page Follows]

 

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WITNESS the execution of this
Agreement as of the date first above written.

 

	 	MOUNT RAINIER
    ACQUISITION CORP.
	 	 
	 	By:	 
	 	 	Name: Matthew Kearney
	 	 	Title: Chief Executive Officer
	 	 
	 	AMERICAN STOCK
    TRANSFER & TRUST COMPANY, LLC
	 	 
	 	By:	 
	 		Name:	
	 	 	Title: 	Vice President
	 	 
	 	INITIAL
    STOCKHOLDERS:
	 	 
	 	DC
    RAINIER SPV LLC

	 	By:	 Dominion Capital LLC, its Manager
	 	By: 	Dominion Capital Holdings LLC, its Manager

 

	 	 	By:	                                            
	 	 	Name:	 
	 	 	Title:	 
	 	 	 
	 	 	A.G.P./Alliance
    Global Partners
	 	 	By:
	 	 	 
	 	 	By:	 
	 	 	Name:	 
	 	 	Title:	 
	 	 	 
	 	 	 
	 	 	Matthew
    Kearney
	 	 	 
	 	 	 
	 	 	Young
    Cho
	 	 	 
	 	 	 
	 	 	Otto
    Risbakk
	 	 	 
	 	 	 
	 	 	Christina
    Favilla
	 	 	 
	 	 	 
	 	 	Jeffery
    Bistrong

 

[Signature Page to Escrow
Agreement]

 

     

     

    

 

EXHIBIT A

 

Initial Stockholders; Escrow Shares

 

	Name
    of Initial Stockholders*	 	Number

    of Shares	 	Date
    of

    Insider Letter 
	DC Rainier
    SPV LLC	 	2,851,919	 	 
	A.G.P./Alliance
    Global Partners	 	965,000	 	 
	Matthew
    Kearney	 	336,985	 	 
	Young
    Cho	 	101,095	 	 
	Otto
    Risbakk	 	19,167	 	 
	Christina
    Favilla	 	19,167	 	 
	Jeffery Bistrong	 	19,167	 	 

 

     

     

    

 

EXHIBIT B

 

Escrow Shares subject to cancellation

 

	DC Rainier SPV LLC	332,859
	A.G.P./Alliance Global Partners	165,000
	Matthew Kearney	43,955
	Young Cho	13,186
	Otto Risbakk	2,500
	Christina Favilla	2,500
	Jeffery Bistrong	2,500

 

     

     

    

 

EXHIBIT C

 

Insider Letter

 

Insider Letter by and between the Company, DC
Rainier SPV LLC, A.G.P./Alliance Global Partners, Matthew Kearney, Young Cho, Otto
Risbakk, Christina Favilla, and Jeffery Bistrong, dated [●], 2021.Exhibit 10.7

 

Mount Rainier Acquisition Corp.

256 W. 38th Street, 15th Floor

New York, NY 10018

[●], 2021

DC Rainier SPV LLC

501 Silverside Road, Suite 102

Wilmington, Delaware 19809

 

Re: Administrative Services Agreement

 

Ladies and Gentlemen:

 

This letter agreement by and
between Mount Rainier Acquisition Corp., a Delaware corporation (the “Company”) and Dominion Capital LLC, a Delaware
limited liability company (“DC LLC”) will confirm our agreement that, commencing on the date the securities of the
Company are first listed on The Nasdaq Global Market (the “Listing Date”), pursuant to a Registration Statement on
Form S-1 (Registration No. 333-[ ]) and related prospectus filed with the U.S. Securities and Exchange Commission (the “Registration
Statement”) and continuing until the earlier of the consummation by the Company of an initial business combination (as defined
in the Registration Statement) or the Company’s liquidation (in each case as described in the Registration Statement) (such earlier
date hereinafter referred to as the “Termination Date”):

 

(i) DC LLC shall make available,
or cause to be made available, to the Company, at 256 W. 38th Street, 15th Floor New York, NY 10018 (or any successor location of DC LLC),
certain office space, utilities and secretarial and administrative support as may be reasonably required by the Company. In exchange therefor,
the Company shall pay DC LLC the sum of $10,000 per month payable commencing on the Listing Date and continuing monthly thereafter until
the Termination Date. DC LLC agrees that payment of such amounts will be deferred, without interest, until the date of consummation by
the Company of the initial Business Combination; and

 

(ii) DC LLC hereby irrevocably
waives any and all right, title, interest, causes of action and claims of any kind as a result of, or arising out of, this letter agreement
in or to, and any and all right to seek payment of any amounts due to it (each, a “Claim”) out of, the trust account
established for the benefit of the public stockholders of the Company and into which substantially all of the proceeds of the Company’s
initial public offering will be deposited (the “Trust Account”), and hereby irrevocably waives any Claim it may have
in the future, which Claim would reduce, encumber or otherwise adversely affect the Trust Account or any monies or other assets in the
Trust Account, and further agrees not to seek recourse, reimbursement, payment or satisfaction of any Claim against the Trust Account
or any monies or other assets in the Trust Account for any reason whatsoever.

 

This letter agreement constitutes
the entire agreement and understanding of the parties hereto in respect of its subject matter and supersedes all prior understandings,
agreements, or representations by or among the parties hereto, written or oral, to the extent they relate in any way to the subject matter
hereof or the transactions contemplated hereby.

 

This letter agreement may
not be amended, modified or waived as to any particular provision, except by a written instrument executed by the parties hereto. 

 

No party hereto may assign
either this letter agreement or any of its rights, interests, or obligations hereunder without the prior written approval of the other
party. Any purported assignment in violation of this paragraph shall be void and ineffectual and shall not operate to transfer or assign
any interest or title to the purported assignee.

 

     

     

    

 

This letter agreement constitutes
the entire relationship of the parties hereto, and any litigation between the parties (whether grounded in contract, tort, statute, law
or equity) shall be governed by, construed in accordance with, and interpreted pursuant to the laws of the State of New York, without
giving effect to its choice of law principles.

 

[Signature Page Follows]

 

    2 

     

    

 

	 	Very truly yours,

 

	 	MOUNT RAINIER ACQUISITION CORP.  

 

		By:	

		Name:	Matthew
                                            Kearney
		Title:	Chief
                                            Executive Officer

 

	 	AGREED TO AND ACCEPTED BY:

 

	 	DOMINION CAPITAL LLC
	 	By: Dominion Capital Holdings LLC, its Manager

		By:	

		Name:	
		Title:	

 

[Signature Page to Administrative
Services Agreement]

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