The Mound: Omen of Cthulhu Guide | Sanity System Explained

Here's a guide on how the Sanity system and hallucinations work in The Mound: Omen of Cthulhu.

Game Guide by Jubair Baky on Jul 30, 2026

The Sanity system in The Mound: Omen of Cthulhu gradually distorts what you see and hear during an expedition. These hallucinations cannot be prevented completely, but understanding when they appear and how to clear them makes it much easier to avoid attacking teammates, chasing false objects, or losing track of the cart.

Sanity declines as an expedition continues. It is not directly tied to combat, distance travelled, or an exact countdown. Instead, hallucinations begin during early time windows and become more frequent the longer you remain in the jungle. Many changes are applied while you are looking elsewhere, then revealed when you turn back.

Recognize Identity Hallucinations

Sanity can make a teammate appear as an undead enemy or make a hostile creature resemble a member of your crew. Watch the target's behaviour before attacking. A supposed monster that is not attacking you, or that is fighting enemies with a familiar weapon, may actually be a teammate under an altered appearance.

The Mound Omen of Cthulhu Guide Sanity Explained

Watch for Environmental and Object Changes

Hallucinations can make the ox-wagon disappear, transform the ox into a demonic version, turn characters into moving trees, or make enemies and teammates look ghost-like. Flies across your view and localized Blood Rain are also Sanity effects. Object hallucinations are especially dangerous because an apparent Musket may become a useless stick after you collect it.

The Mound Omen of Cthulhu Guide Watch for Environmental and Object Changes

Use Saint Dymphna to Clear Hallucinations

Rescue the Woodworker and return him safely to the Tempestad before using Patron Saints. You must then recover the Saint Dymphna Sacred Figure from Cliffs of Ibarra - North and have the Woodworker create the larger statue. Equip Saint Dymphna on the ox-wagon before starting an expedition.

When hallucinations become disruptive, return to the ox-wagon and use the prayer prompt at the statue. Saint Dymphna dispels active altered states of the spirit. This clears the hallucinations affecting you at that moment, but it does not stop the Sanity system from continuing in the background or prevent new effects later in the expedition.

The Mound Omen of Cthulhu Guide Use Saint Dymphna to Clear Hallucinations

Break or Wait Out Individual Effects

Sanity cannot be stopped permanently, but active hallucinations can expire, break through interaction, or be cleansed by praying to Saint Dymphna.

Some hallucinations disappear naturally, while others break after an interaction. Placing an item into an invisible ox-wagon can restore its appearance. Striking a teammate may also break an altered appearance, but this damages health and Armour, so communication and observation are safer whenever possible.