The Mound: Omen of Cthulhu’s Free Halloween Update Unleashes Tsathoggua on Xbox

The Mound: Omen of Cthulhu has a free Halloween update on Xbox. The Cult of Tsathoggua adds a new quest, an underground lair ruled by a giant amphibian Great Old One, cursed treasures, new weapons and a reworked progression system with a level cap of 70.

The update is out now on Xbox Series X|S. It’s the latest in a run of updates for ACE Team’s co-op horror game since NACON released it on 15 July 2026, and NACON has released a new trailer to go with it.

A new quest leads to Tsathoggua’s Lair

Once you’ve unlocked the southern regions, a prisoner chained on the lower deck of the galleon sends you looking for the Shrine of Tsathoggua. To get there you need six Eyes of Tsathoggua, hidden inside shrines during Treasure Hunt missions. You can find one per expedition, on any map, and Eyes lost during an expedition don’t count. Eyes collected as a guest in someone else’s game count towards your own progress.

Bring six back to the galleon and Tsathoggua’s Lair opens up. The new underground map is home to Tsathoggua, a colossal creature that conventional weapons can’t hurt, so you’ll need to work out another way to beat it. Torches, salts and healing supplies are scattered around the lair, and only the host needs to have unlocked the map for the whole group to join.

Beating Tsathoggua earns everyone in the group the Eye of Servitude, a new occult relic that turns monsters against their own kind when you hold it up to them. A new Frog-Fishman enemy lives in the lair and on some maps near the Mound, and new tentacle threats appear in Portal Contracts.

Cursed treasures and new weapons

Treasure Shrines now hold cursed treasures: valuable-looking items with a nasty effect on whoever carries them. They’re flagged with a red flash in your inventory, a sound and an on-screen warning.

• Screaming Idol: makes noise while you carry it.
• The Trees Will Listen: nearby trees turn hostile and attack you with their branches.
• Mi-Go’s Beacon: draws a Mi-Go to you, and holding on to it can bring another.
• Blood Price: cuts your maximum health by half.

On the weapons side, the Swivel Breech Flintlock fires two shots before it needs reloading, and a Hand Grenade is now sold in the shop.

Level cap raised to 70 with a new skill tree

The maximum rank goes up to 70, and progression now runs through a new skill tree. You earn one skill point per rank, spend points at the statue aboard the galleon, and pick one perk per row. You can reset the tree at any time to get your points back.

New perks include two tiers of bleed resistance, stamina boosts to 125% and then 150%, carrying bodies without slowing down, a faint glow for seeing in the dark, immunity to red dust parasites, a knife that never breaks and silent running in armour.

Sanity effects have been expanded too, with one of the existing hallucinations now extended to new items, and your teammates may not see the same thing you do. The galleon has also been decorated for Halloween.

For the full rundown, read everything we know about The Mound: Omen of Cthulhu, and find all our coverage on The Mound: Omen of Cthulhu hub.

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