Monsters immune to damage if in Fog

[Sianist]

just noticed something that doesn't make sense ...

I've thrown a etl6.5 Fireflash into a group of snakes in old forests guessing that the whole meadow i'm throwing it into is full of snakes ... yet only those snakes i can see is harmed (well ... killed), while those just outside my view (yet clearly within the explosion) is unharmed.

Doesn't make sense that.

Edit:

even if monsters are seen by Arcane eye, they don't take damage if they aren't in Line of effect from your character

[SageAcrin]

The In Vault status is applied to various enemies that are in pregenerated special rooms. This makes them immobile-and immune to damage-until you see them.

This includes "monster nest" type vaults, which include those big boxes full of snakes/ants you see in Old Forest.

[String]

Maybe that invulnerability status should be revoked if the monster gets detected by arcane eye, telepathy, tracking, etc as well as LOS? )