Document:

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                                                                   EXHIBIT 10.13
[LOGO] intermedia
       COMMUNICATIONS

June 29, 1999

Mr. Mark Shull
1123 Lexington Place Ridge Drive
Lexington, MA 02173

Dear Mark:

It is with great pleasure that I offer you the position of Senior Vice
President, Intermedia Communications Inc. (the "Company"), and President and
CEO of DIGEX, Incorporated ("DIGEX"). We anticipate that you will accept this
offer and officially assume this position on or before July 1, 1999.

This is an important officer position within the company that reports directly
to David C. Ruberg, Chairman, President and CEO. Your annual base salary will be
$250,000 (based on 52 weeks service). This will be reviewed again on January 1,
2000.

This position has an annual management incentive compensation target
opportunity of 50% of base salary ($125,000). This bonus opportunity is
contingent upon the achievement of shared corporate objectives as well as the
achievement of two to five individual objectives that relate to your primary
responsibilities. You are expected to establish these individual objectives,
with my approval.

This offer also includes a stock option grant covering 200,000 shares of
Intermedia common stock, subject to approval by the Compensation Committee of
the Board of Directors. This grant will vest in equal installments over the 60-
month period commencing with the date of your employment by the Company, subject
to customary terms contained in the standard incentive stock options issued by
the Company under this Plan. For pricing purposes, the date of the grant will be
deemed to be the date upon which the options have been approved by the
Compensation Committee of the Board of Directors. Following the occurrence of a
change of control of the Company, all unvested installments of the options
will vest if your employment is terminated by the Company (other than for
cause as defined herein) or, if earlier, one year following the date of
occurrence of the change of control if you continue to be employed by the
Company at that date.

For the purposes of the preceding sentence and otherwise contained
herein, "Change of Control" means the sale, exchange or transfer of common stock
of the Company or of DIGEX, whether in one transaction or a series of related
transactions occurring within one year, which results in an accumulation of
50% or more of the outstanding shares of common stock (on fully diluted basis)
or of DIGEX in one holder or several affiliated holders (or any such
transaction(s) occurring within six months that result in an accumulation of
at least 35% of such shares of common stock (on a fully diluted basis)) or an
event involving the sale or merger of the Company or of DIGEX or their
respective assets which results in the holders of shares of common stock
immediately prior to the

<PAGE>

Mark Shull
Offer Letter
Page 2

occurrence of such sale or merger holding less than a majority of the
outstanding shares of common stock immediately thereafter.

As you know, DIGEX has filed a registration statement covering an initial public
offering of its common stock (the "DIGEX Common Stock"). If the public offering
occurs within one year of the date of your acceptance of this offer, you will
relinquish your title as a senior vice president of the Company and, to the
extent not previously vested, your Company stock options will be canceled and
will be replaced by options to purchase 400,000 shares of DIGEX Common Stock (or
that number of shares of DIGEX Common stock as shall equal 1% of DIGEX's total
outstanding shares of Common Stock immediately following the offering if more or
less than 40 million shares are outstanding at that date), 200,000 of which will
be exercisable at $5.00 per share and the balance of which will be exercisable
at the initial public offering price. Options covering 25% of the shares of
DIGEX Common Stock will vest one year following the date of grant and the
balance will vest in equal quarterly installments over the next three years. If
a change of control occurs, options covering one-half of the shares will vest
immediately and the balance will vest in accordance with the last sentence of
the preceding paragraph. You will also become a member of the Board of Directors
of DIGEX upon consummation of the initial public offering.

If your employment with the Company or DIGEX is terminated by the Company or
DIGEX for any reason other than for cause (described below), the Company or
DIGEX will pay your base salary as in effect at the time of termination through
the later of July 1, 2001, or for one year following the date of termination,
payable either on the same dates it would have been paid had your employment
continued through such later date or in a lump sum, as the Company or DIGEX
decides. If your termination occurred following the occurrence of a Change of
Control, you will be paid in a lump sum promptly following such termination.
Your entitlement to receive payments shall terminate and cease to be of any
force or effect in the event you, directly or indirectly (whether by an entity
of which you own greater than 10% of the outstanding equity interest or by which
you are employed in a senior executive capacity) knowingly hire within six
months following your date of termination, any employee of Director level or
above of the Company or DIGEX, who was employed by the Company or DIGEX on the
date of your termination. Cause means (i) any conduct or behavior by you that
would reasonably be expected to have a material adverse effect on the Company's
or DIGEX's business or reputation, (ii) commission by you of an act involving
moral turpitude or dishonesty, including fraud, (iii) your material failure to
reasonably perform your duties for DIGEX or (iv) your willful failure to perform
or abide by any lawful directions or instructions of DIGEX or the Company
consistent with your capacity as a senior executive of the DIGEX.

Notwithstanding anything in this letter to the contrary, if it shall be
determined that any payment or distribution by the Company or of DIGEX to or for
your benefit (whether paid or payable or distributed or distributable pursuant
to the terms of this letter or otherwise) (a "Payment") would constitute an
"excess purchase payment" within the meaning of Section 4999 of the internal
revenue code, that the Payments, in the aggregate, shall be reduced (in a manner
elected by you, or by the Company or DIGEX if you fail to make such an election)
to the greatest amount that could be paid to you so that no portion thereof
shall be subject to the excise taxes imposed by Section 4999 of the internal
revenue code.

<PAGE>

Mark Shull
Offer Letter
Page 3

As an employee of DIGEX, you will be entitled to all employee benefits: Medical
insurance, prescription drug card, dental insurance, long-term disability, life
insurance, 401(k) Plan, educational reimbursement, holidays, sick leave,
military leave, bereavement leave, voting time off and jury duty leave, and
supplemental executive life insurance. Assuming you start on or before July 1,
1999, your medical benefits will be effective July 1, 1999. You will be eligible
for 3 weeks of paid vacation per year, upon your first year of employment. This
will increase to 4 weeks on January 1 of the year following the 10th anniversary
from your date of hire.

This offer includes a relocation allowance of up to $100,000. Subject to this
limit, you will be reimbursed for relocation expenses (documented by receipts)
in accordance with the Company's Relocation Policy, a copy of which will be
provided to you. Reimbursable expenses include items such as transportation
of you and your family, movement of household goods, real estate commission for
the sale of the old home, closing costs associated with the purchase of the
new home, incidental expenses and house hunting trips. DIGEX will "gross up" the
taxable elements of this reimbursement. The "gross-up" is not considered part of
the relocation allowance.

In order that we demonstrate our sensitivity to individual needs during the
relocation period, you will note in the description of the relocation policy
that DIGEX may also provide temporary housing expenses for a period of up to six
months, separate from the relocation allowance itself. This is subject to
advance agreement with your supervisor and normally includes the provision of a
furnished apartment facility in Beltsville and reimbursement of up to two
trips per month during the relocation period between Beltsville and your former
residence.

This relocation assistance and temporary housing will be forgotten over a
12-month period at a rate of 1/12 per month, commencing on the date of your
last relocation reimbursement. If you voluntarily terminate your employment with
DIGEX prior to the end of this 12-month period, the relocation balance that
exceeds the forgiven amount must be repaid to DIGEX.

We sincerely believe that Intermedia and DIGEX have an exciting future, filled
with substantial opportunity for business growth and success. We also feel that
you are a very talented person with significant potential to help us grow and
succeed. We are excited about the prospect of you joining the Intermedia team.

Sincerely,

/s/ David C. Ruberg

David C. Ruberg
Chairman, President and CEO

By signing below I accept this offer.

/s/ Mark Shull                          6/29/99
--------------------------------        -------
Signature                               Date:
<PAGE>

Intermedia
COMMUNICATIONS

                                                                   July 9, 1999

Mr. Mark Shull
One Digex Plaza
Beltsville, Maryland 20705

Dear Mark:

     This will confirm the changes we have agreed upon in your employment
arrangement with Digex as follows:

     (a) One-half of the then unvested portion of each of your Intermedia
options and Digex options will vest immediately upon the occurrence of a change
of control.

     (b) Your Intermedia stock option has been reduced to cover 100,000 shares
of Intermedia common stock and will continue in full force and effect following
consummation of the Digex initial public offering.

     (c) Your bonus opportunity is 60% of your base salary.

     (d) Your title is President and Chief Executive Officer.

     (e) If an adjustment is required to be made to the shares covered by your
Digex options to equal 1% of the outstanding shares, the adjustment will be made
based upon the number of shares of common stock of Digex outstanding immediately
prior to consummation of the initial public offering. For example, if the number
of the outstanding shares will equal 50 million, then the options will equal
500,000 shares.

     Except as amended hereby, the terms of your original offer letter continue
in full force and effect. If the foregoing is acceptable to you, please sign in
the space provided below and return to me one fully executed copy of this
letter. Nothing in this letter will be deemed to affect the at will status of
your continued employment by Digex.

                                          DIGEX INCORPORATED

                                          By: /s/ David C. Ruberg
                                          -------------------------------
                                              David C. Ruberg, Chairman

Agreement with terms
of letter confirmed:

/s/ Mark Shull
-----------------------
Mark Shull

3625 Queen Palm Drive, Tampa, Florida 33619      Main Line 813 829.0011
Toll Free 800 940.0011                               www.intermedia.com<PAGE>

                                                                   Exhibit 10.14

  [LOGO]
intermedia
COMMUNICATIONS

       December 14, 1998

       Ms. Nancy Faigen
       35 Wicks End
       Wilton, Connecticut 06897

       Dear Nancy:

       It is with great pleasure that I offer you the position of President and
       General Manager, WebSite Management Division with Intermedia
       Communications Inc., located in Beltsville, Maryland. We anticipate that
       you will accept this offer immediately, and officially assume this
       position on December 14, 1998.

       This is an important officer position within the Company, which reports
       directly to Jim Geiger, Senior Vice President, Chief Marketing Officer.
       The annual base salary is $225,000 (based on 52 weeks service). We
       recognize that by accepting this position and starting with us
       immediately, you will forego a substantial amount of compensation and
       other benefits from your former employer. In order to offset the
       financial impact to you and in recognition of your commitment to us, we
       are pleased to offer you a signing bonus to be dispensed as follows:

       .  A $125,000 signing bonus will be provided in two installment: $50,000
          on January 2, 1999 and $75,000 on August 1, 1999. This amount is
          guaranteed without restrictions or requirements.

       .  An additional $150,000 signing bonus will be provided in two
          installments: $50 000 on the date you accept this offer and the
          remaining $100,000 will paid on April 1, 1999 provided you are still
          employed with us on that date.

        In recognition of our commitment to you, we do ask that you warrant, by
        your acceptance of this position and the associated bonus, that you are
        not subject to or a party to any agreement with your former employer
        that would restrict or otherwise prohibit you from accepting this
        position with Intermedia.

        In addition, this position has an annual management incentive
        compensation target opportunity of 45% of base salary ($101,250). For
        1999, you will be eligible for this entire bonus opportunity, based on
        performance. This bonus opportunity is contingent upon the achievement
        of revenue, server units in service, EBITDA, capital expenditure, and
        headcount. You will be eligible for a performance and salary review on
        January 1, 2000.

        This offer includes a stock option grant covering 100,000 shares of
        common stock subject to approval by the Compensation Commitee of the
        Board of Directors. This grant will vest in equal installments over the
        60-month period commencing with the date of your employment by the
        Company, subject to customary terms contained in the standard incentive
        stock options issued by the Company under the Plan. For pricing
        purposes, the date of the grant will be deemed to be the date upon which
        the option has bean approved by the Compensation Committee of the Board
        of Directors. This grant will immediately vest upon a change in control
        of the Company, if followed by termination of your employment with the
        Company under certain conditions within twelve months thereafter.

        As an employee of Intermedia, you will be entitled to all employee
        benefits: Medical insurance, medical and prescription drug card, dental
        insurance, short-term and long-term disability, life insurance, 401(k)
        Plan, educational reimbursement, holidays, sick leave, military leave,
        bereavement leave, voting time off and jury duty leave, and supplemental
        executive life insurance. Assuming you start on December 14, 1998 your
        medical benefits will be effective January 1, 1999. You will be eligible
        for 3 weeks of paid vacation per year, including your first year of
        employment.
<PAGE>

        Page Two
        December 14, 1998

        This offer includes a relocation allowance of up to $125,000. Subject to
        this limit, you will be reimbursed for relocation expenses (documented
        by receipts) in accordance with Intermedia's Relocation Policy, a copy
        of which is attached. Reimbursable expenses include items such as
        transportation of you and you family, movement of household goods, real
        estate commission for the sale of the old home, closing costs associated
        with the purchase of the new home, incidental expenses and house hunting
        trips. The Company will "gross up" the taxable elements of this
        reimbursement. The "gross up" is not considered part of the relocation
        allowance.

        In order that we demonstrate our sensitivity to individual needs during
        the relocation period, you will note in the description of the
        relocation policy that the Company may also provide temporary housing
        expenses for a period of up to six months, separate from the relocation
        allowance itself. This is subject to advance agreement with your
        supervisor and normally includes the provision of a furnished apartment
        facility in Maryland and reimbursement of up to two trips per month
        during the relocation period between Maryland and your former residence.
        Individual needs vary greatly, so please discuss your specific needs
        with Jim Geiger.

        This relocation allowance and temporary housing expenses wi1l be
        forgiven over a 12-month period at a rate of 1/12 per month, commencing
        on the date of your last relocation reimbursement. If you voluntarily
        terminate your employment with Intermedia prior to the end of this
        12-month period, the relocation balance that exceeds the forgiven amount
        must be repaid to the Company.

        Please contact Lois Durham, Human Resources, (813) 829-4518, to commence
        the administration of your relocation.

        Nancy, we sincerely believe that Intermedia has an exciting future,
        filled with substantial opportunity for business growth and success. We
        also feel that you are a very talented person with significant potential
        to help us grow and succeed. We are excited about the prospect of you
        joining the Intermidia team.

        Sincerely.

        /s/ David C. Ruberg

        David C. Ruberg
        President and CEO

        Attachments

        By signing below I accept this offer.

        /s/ Nancy G. Faigen           12/14/98
        ----------------------        --------
        Signature                     Date

        Please return the signed offer 1etter and relocation agreement to Trevor
        Dignall, Senior Vice President, Human Resources, in the enclosed, pre-
        addressed envelope.
<PAGE>

Digex keeps e-business in business(SM)           [LOGO] digex(SM)

                                                            One Digex Plaza
                                                            Beltsville, MD 20705
                                                            www.digex.com

                                                            301.847.5000
                                                            Fax 301.847.5215

                                       July 9, 1999

   Ms. Nancy G. Faigen
   One Digex Plaza
   Beltsville, Maryland 20705

   Dear Nancy:

             This will confirm the changes we have agreed upon in your
   employment arrangement with Digex as follows:

             (a) Your base salary is $225,000 per year and your annual bonus
   opportunity is 50% of your base salary.

             (b) If the pending initial public offering of Digex common stock
   becomes effective, you will be granted Digex stock options covering an
   aggregate of 300,000 shares of common stock. The options will be exercisable
   as to 50% of the shares at an exercise price equal to $5.00 per share and as
   to the balance of the shares, at an exercise price equal to the initial
   public offering price. Options covering 25% of the shares will vest one year
   following the date of grant and the balance will vest in equal quarterly
   installments over the next three years so long as you continue to be employed
   by Digex. Following the occurrence of a change of control, all unvested
   installments of the options will vest if your employment is terminated by
   Digex (other than for cause as defined herein) or, if earlier, one year
   following the date of occurrence of the change of control if you continue to
   be employed by Digex at that time.

             (c) Your title will be President, Sales and Service Delivery Group
   of Digex.

             (d) Your existing Intermedia stock options shall continue in full
   force and effect following consummation of the initial public offering of
   Digex common stock.

             For purposes of this letter:

             "Change of Control" means: the sale, exchange or transfer of common
             stock of Intermedia or of Digex, whether in one transaction or a
             series of related transactions occurring within one year, which
             results in an accumulation of 50% or more of the outstanding shares
             of common stock (on a fully diluted basis) of
<PAGE>

Digex keeps e-business in business(SM)           [LOGO] digex

                                                            One Digex Plaza
                                                            Beltsville, MD 20705
                                                            www.digex.com

                                                            301.847.5000
                                                            Fax 301.847.5215

             Intermedia or of Digex in one holder or several affiliated holders
             (or any such transaction(s) occurring within six months that result
             in an accumulation of at least 35% of such shares of common stock
             (on a fully diluted basis)) or an event involving the sale or
             merger of Intermedia or of Digex or their respective assets which
             results in the holders of shares of common stock immediately prior
             to the occurrence of such sale or merger holding less than a
             majority of the outstanding shares of common stock immediately
             thereafter.

             "Cause" means: (i) any conduct or behavior by you that would
             reasonably be expected to have a material adverse affect on
             Intermedia's or Digex's business or reputation, (ii) commission by
             you of an act involving moral turpitude or dishonesty, including
             fraud, (iii) your material failure to reasonably perform your
             duties for Digex or (iv) your willful failure to perform or abide
             by any lawful directions or instructions of Digex consistent with
             your capacity as a senior executive of Digex.

             Except as amended hereby, the terms of your original offer letter
   continue in full force and effect. If the foregoing is acceptable to you,
   please sign in the space provided below and return to me one fully executed
   copy of this letter. Nothing in this letter will be deemed to affect the at
   will status of your continued employment by Digex.

                                       DIGEX, INCORPORATED

                                       By:/S/ Mark Shull
                                          ----------------------------------
                                          Mark Shull, President and Chief
                                            Executive Officer

   Agreement with terms
   of letter confirmed:

   /S/ Nancy Faigen
   ----------------------------------
   Nancy G. Faigen

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