Company: SBXD
Filing Date: 2025-11-06
Form Type: 425
Source: 0001104659-25-107354
Chunk: 1

Company: SilverBox Corp IV
Filing Date: 2025-11-06
Form: 425
Chunk 1
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emable Warrants included as part of the units, each whole warrant exercisable for one Class A ordinary share at an exercise price of $11.50 |     | SBXD.WS   |     | New York Stock Exchange LLC |

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter).

Emerging growth company x

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ¨

Item 1.01 Entry into a Material Definitive Agreement.

Amendment to the Preferred Equity Subscription Agreements

As previously disclosed, Parataxis Holdings Inc.,
a Delaware corporation (“Pubco”), Parataxis Holdings LLC, a Delaware limited liability company (the “Company”)
and certain accredited investors (the “Preferred Equity Investors”) entered into agreements (the “Preferred Equity Subscription Agreements”) on August 6, 2025, pursuant to which, the Company agreed to issue, and the Preferred Equity
Investors agreed to purchase, an aggregate of 3,100,000 preferred equity units of the Company, in a private placement, at a purchase price
of $10.00 per unit for an aggregate purchase price of $31,000,000, (the “Preferred Equity Investments”).

On October 31, 2025, Pubco, the Company, and
the Preferred Equity Investors amended the Preferred Equity Subscription Agreements, to (i) eliminate the provisions prohibiting
the Company from pledging, hypothecating or otherwise encumbering the Bitcoin purchased with the proceeds from the Preferred Equity Investments,
and (ii) permit the Company to pledge, grant as security, create liens or charges, collaterally assign, encumber, hypothecate or
otherwise use such Bitcoin as collateral or other credit support to secure any indebtedness or obligations pursuant to lending or other
financing arrangements.

Important Information

This Current Report on Form 8-K is being made in respect of the proposed business combination (the “Business Combination”) and the other transactions contemplated by the Business Combination Agreement among SilverBox Corp IV (“SBXD”), Parataxis Holdings LLC (“Parataxis