Company: SBXD
Filing Date: 2025-12-04
Form Type: 425
Source: 0001104659-25-118461
Chunk: 1

Company: SilverBox Corp IV
Filing Date: 2025-12-04
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 8.01 Other Events.

On December 4, 2025, Parataxis Holdings LLC (“Parataxis Holdings” or the “Company”) issued a press release announcing that it, together with other affiliated entities, has entered into a definitive agreement with Sinsiway Co. Ltd. (“Sinsiway”)(KOSDAQ: 290560) in a transaction valued up to KRW 35 billion, which would result in Parataxis Holdings holding a controlling interest in Sinsiway (the “Transaction”). Following the closing of the Transaction, Sinsiway intends to change its corporate name to Parataxis ETH, Inc. and remain listed on the KOSDAQ. The Transaction is subject to certain closing conditions.

The Transaction would result in the creation of South Korea’s first Ethereum-based treasury platform listed on South Korean public markets, that is anchored by US-based institutional investors with significant experience in managing digital asset investments.

Item 9.01 Financial Statements and Exhibits.

(d) Exhibits.

| Exhibit 
 No.     
 99.1    |     | Description                                                                 
 Press Release of Parataxis Holdings LLC dated December 4, 2025              |
|:--------|:----|:----------------------------------------------------------------------------|
| 104     |     | Cover Page Interactive Data File (embedded within the Inline XBRL document) |

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 , and Parataxis Holdings Inc., a holding company that will become the publicly listed company (“PubCo