What players often call Space Marine 2’s “Horde Mode” is officially named Siege, and it is already live. The latest addition, Chaos Siege, arrived in Patch 15 on October 1, 2026, letting players fight as Chaos Space Marines in two new sectors on Avarax.
What is Space Marine 2’s Horde Mode?
Siege is a cooperative PvE survival mode in which players defend an Imperial fortress on Kadaku from increasingly dangerous waves of Tyranid and Chaos forces. Focus Entertainment announced it as a three-player mode and released it as a free update on June 26, 2025. Focus Entertainment’s Siege announcement describes the original setup.
The original Siege mode remains distinct from the newer Chaos Siege addition: it puts Space Marines on the defending side, while Chaos Siege lets players take control of Chaos Space Marines.
What does Chaos Siege add?
Patch 15, also called Anniversary Update II, launched on October 1, 2026, and added Chaos Siege. It introduces two new Siege sectors on Avarax, where Chaos Space Marines face Tyranids, Cadians, and loyalist Space Marines. The official announcement confirms the playable side, opposing factions, and sectors, but does not provide a complete wave-by-wave ruleset or establish that Chaos Siege uses the original mode’s three-player limit. Focus Entertainment’s Patch 15 announcement lists the update’s details.
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#1 Best Overall
- Embody the superhuman skill and brutality of a Space Marine. Unleash deadly abilities and devastating weaponry to obliterate the relentless Tyranid swarms. Defend the Imperium in spectacular third-person action in solo or co-op modes.
- Purge the relentless Tyranid swarms as legendary Space Marine Titus in a spectacular new campaign. Play solo or with up to 2 friends in 3 player co-op.
- Enjoy intense, gory and fast-paced third-person action with hundreds of enemies on screen, from the creators of blockbuster co-op shooter World War Z.
- Standard edition includes: Base game, Macragge’s Chosen DLC, with 3 unique cosmetics for your Bolt Rifle, Chainsword & Power Armour
Siege and Chaos Siege compared
| Detail | Original Siege | Chaos Siege |
|---|---|---|
| Availability | Released June 26, 2025, as a free update; Focus Entertainment, May 22, 2025 | Released October 1, 2026, in free Patch 15; Focus Entertainment, October 1, 2026 |
| Setting | Kadaku; defend an Imperial fortress | Two new Siege sectors on Avarax |
| Player side | Space Marines | Chaos Space Marines (Heretic Astartes) |
| Opposition | Tyranid and Chaos forces | Tyranids, Cadians, and loyalist Space Marines |
| Confirmed format | Three-player survival against endless, increasingly dangerous waves | PvE; player count and a full wave ruleset not stated in the announcement |
What changed before Patch 15?
Siege had already received a substantial update in May 2026. The Purgation Update revamped the mode’s progression and added the Hive Tyrant and Mutalith Vortex Beast. Focus Entertainment’s Purgation Update announcement covers those changes; Warhammer Community also reported new rewards, mission modifiers, and boss-level enemies in its May 21, 2026 Skulls Festival coverage. These were Purgation-era additions, not features first introduced by Patch 15.
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Focus Entertainment says Patch 15 is available on PlayStation 5, Xbox Series X|S, and PC, and describes the update as free for players on those supported platforms. Siege is content for Space Marine 2, not a separately purchased mode. The original mode was likewise announced as a free update for PlayStation 5, Xbox Series, and PC.
Quick Recap
Rank #4
- Includes 2 multipart plastic Space Marines Intercessor miniatures with distinct poses. Also includes a Starter paint brush
- Paints include – - 1 Abaddon Black (Base) – 1 Macragge Blue (Base) – 1 Mournfang Brown (Base) – 1 Leadbelcher (Base) – 1 Retributor Armour (Base) – 1 Corax White (Base)
- These miniatures are unpainted and need to be assembled. We recommend using Citadel Plastic Glue and Citadel Paints.
Rank #3
- Brand new. UK Import PAL version. Game in English. UK PSN account may be required for any online features.
Rank #2
- Purge the relentless Tyranid swarms as legendary Space Marine Titus in a spectacular new campaign. Play solo or with up to 2 friends in 3 player co-op.
- Enjoy intense, gory and fast-paced third-person action with hundreds of enemies on screen, from the creators of blockbuster co-op shooter World War Z.
- Defend the Imperium as your own Space Marine in an endlessly brutal and replayable PvE missions up to 3 players featuring 6 classes, unlocking new skills and cosmetics.
- Wage eternal war on your enemies in ferocious 6v6 PvP matches and bring glory to your faction!
- The Ultima Limited Edition contains: Warhammer 40,000: Space Marine 2, SteelBook case with exclusive artwork, Season Pass 1, Season Pass 2, Macragge's Chosen DLC
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