Horizon Copper Reminds Shareholders and Warrantholders to Vote in Advance of the Upcoming Special Meeting of Securityholders

• The deadline to vote your shares and warrants is October 7, 2025 at 8:00 AM Vancouver Time.
• Your vote is important no matter how many Horizon Copper shares and/or warrants you hold.
• The Board of Directors of Horizon Copper recommends that Securityholders vote FOR the Arrangement Resolution.
• For assistance in voting, please contact Laurel Hill Advisory Group by phone at 1-877-452-7184 (North American toll-free) or 1-416-304-0211 (outside North America ), or by email at assistance@laurelhill.com

Horizon Copper Corp. (TSXV: HCU), (OTCQB: HNCUF) ("Horizon Copper", "Horizon", or the "Company") reminds its shareholders and warrantholders (together, "Securityholders") to vote ahead of the proxy voting deadline for the upcoming Special Meeting of Securityholders (the "Meeting"). At the Meeting, Securityholders will be asked to pass a special resolution (the "Arrangement Resolution") approving an arrangement involving Horizon, Royal Gold Inc. ("Royal Gold") and International Royalty Corporation, a wholly-owned Canadian subsidiary of Royal Gold ("AcquireCo"), whereby Royal Gold will indirectly through AcquireCo acquire all of the issued and outstanding Horizon shares (other than those held by Sandstorm Gold Ltd. ("Sandstorm")) and through Horizon acquire all of the outstanding Horizon warrants (the "Horizon Transaction").

The Board of Directors of Horizon unanimously recommends that the Securityholders vote FOR the Arrangement Resolution.

Other Updates

Royal Gold has announced that it has received all government regulatory approvals required for the Horizon Transaction and for Royal Gold's previously announced acquisition of Sandstorm.

The completion of the Horizon Transaction is subject to customary closing conditions, including, without limitation, the approvals by Securityholders described above and the approval of the Supreme Court of British Columbia . Subject to the satisfaction or waiver of the closing conditions, it is anticipated that the Horizon Transaction will close early in the fourth quarter of 2025.

Meeting Details

The Meeting is to be held on October 9, 2025 at 8:00 a.m. ( Vancouver time) in the Copper Boardroom at the Company's head office located at Suite 3200, 733 Seymour Street, Vancouver, British Columbia , Canada V6B 0S6. Please visit Horizon's website at www.horizoncopper.com/special-meeting for complete details and links to all relevant documents ahead of the Meeting.

The deadline for voting by proxy is 8:00 a.m. ( Vancouver time) on October 7, 2025 .

In light of the current Canada Post strike, Securityholders are strongly encouraged to cast their votes online. If you have mailed in your vote, we suggest that you recast your vote online to ensure your instructions are received in a timely manner. Securityholders who require voting assistance may contact Horizon's proxy solicitation agent, Laurel Hill Advisory Group at the number below.

While the Canada Post strike is ongoing, Registered Securityholders who wish to deposit their letters of transmittal, share certificates and other required documentation, as applicable, should use courier services or hand deliver such documentation to the depositary, Computershare Investor Services Inc., at 320 Bay Street, 14th Floor, Toronto, Ontario M5H 4A6.

Questions & Voting Assistance

Securityholders who have questions about the Meeting or require assistance in voting may contact the Company's proxy solicitation agent:

Laurel Hill Advisory Group

North American Toll Free | 1-877-452-7184

Outside North America | 1-416-304-0211

By Email | assistance@laurelhill.com

How to Vote

About Horizon Copper

Horizon Copper is a premier copper company holding a portfolio of unparalleled copper assets, including a 1.66% net profits interest on the Antamina copper mine, exposure to the Oyu Tolgoi copper mine through a 24% equity ownership in Entrée Resources Ltd., and a 30% interest in the copper-gold Hod Maden project. For more information, visit www.horizoncopper.com .

Cautionary Note Regarding Forward-Looking Information

This press release contains forward-looking information within the meaning of Canadian securities laws. Forward-looking statements generally include, but are not limited to, statements with respect to management's beliefs, plans, estimates and intentions, and similar statements concerning the Horizon Transaction, the ability to complete the Horizon Transaction and the other transactions contemplated by the Arrangement Agreement (including the Sandstorm transaction) and the timing thereof, including the parties' ability to satisfy the conditions to the consummation of the Horizon Transaction, the receipt of the required securityholder approvals and court approval and other customary closing conditions, the possibility of any termination of the Arrangement Agreement in accordance with its terms or the Sandstorm transaction, and the expected benefits to Horizon and its securityholders, and other statements that are not historical facts. Although Horizon believes that such information is reasonable, it can give no assurance that such expectations will prove to be correct. Forward-looking information is typically identified by words such as: "believe", "expect", "anticipate", "intend", "estimate", "postulate" and similar expressions, or are those, which, by their nature, refer to future events. The Company cautions investors that any forward-looking information provided by Horizon is not a guarantee of future results or performance and that actual results may differ materially from those in forward-looking information as a result of various factors, including, but not limited to: the possibility that the Horizon Transaction or the Sandstorm transaction will not be completed on their terms and conditions, or on the timing, currently contemplated, and that they may not be completed at all, due to a failure to obtain or satisfy, in a timely manner or otherwise, required securityholder and court approvals and other conditions to the closing of the Horizon Transaction or the Sandstorm transaction or for other reasons; the Sandstorm transaction being completed in a circumstance where the Horizon Transaction is terminated; the negative impact that the failure to complete the Horizon Transaction for any reason could have on the price of the Horizon Shares or on its business; Royal Gold's failure to pay the consideration at closing of the Horizon Transaction; the failure to realize the expected benefits of the Horizon Transaction; the restrictions imposed on Horizon while the Horizon Transaction is pending; significant transaction costs or unknown liabilities; and risks related to the diversion of management's attention from Horizon's ongoing business operations while the Horizon Transaction is pending; and other risks and uncertainties affecting Horizon such as those relating to expected capital expenditures, including exploration and development activity and the future price and demand of gold, copper, and other metals. The forward-looking statements contained in this press release are made as of the date of this press release. Horizon disclaims any intention or obligation to update or revise any forward-looking statements, whether as a result of new information, future events or otherwise, except as required by law. The securities referred to in this press release have not been, nor will they be, registered under the United States Securities Act of 1933, as amended, and may not be offered or sold within the United States or to, or for the account or benefit of, U.S. persons absent U.S. registration or an applicable exemption from the U.S. registration requirements. The Company assumes no obligation to update forward-looking statements except as required under securities laws. Further information concerning risks, assumptions and uncertainties associated with forward-looking statements and our business can be found in Horizon's Annual Information Form for the year ended December 31, 2024 , filed under the Company's profile on SEDAR+ ( www.sedarplus.ca ), as well as subsequent filings that can also be found under the Company's profile.

Neither the TSX Venture Exchange nor its Regulation Services Provider (as that term is defined in the policies of the TSX Venture Exchange) accepts responsibility for the adequacy or accuracy of this release.

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SOURCE Horizon Copper Corp.

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