The Spirit of delirium is a monster Gregorovic summons in his fight if he is near the mask of delirium. It does not attack the player. Upon touching Gregorovic, it will say "Accept the unreal." before disappearing. The spirit increases Gregorovic's poison damage, although this can be easily canceled out with the Venomblood perk, as it makes the player immune to standard poison. It should be killed if the player does not have it as forgetting to drink antipoison can be fatal with his normal attacks. Like the other two spirits, the Spirit of mania and Spirit of rage, multiple spirits of delirium can stack on the poison effect to make Gregorovic's poison damage extremely deadly.