Memory Moss (Hazard, Plant [Fungus]) CR 5
Memory moss appears as a 5-foot square patch of black moss. It grows in temperate or warm climates and is sometimes encountered in subterranean realms. Memory moss cannot abide the cold or the arid clime of the desert and is never encountered in such environments.
When a living creature moves within 60 feet of a patch of memory moss, it attacks by attempting to steal that creature’s memories. It can target a single creature each round. A targeted creature must succeed on a DC 16 Will save or lose all memories from the last 24 hours. This is particularly nasty to spellcasters, who lose all spells prepared within the last 24 hours. (Only those spells actually prepared in the last 24 hours are lost; spells prepared longer than 24 hours ago are not lost.)
Once a memory moss steals a creature’s memories, it sinks back down and does not attack again for one day. If a creature loses its memories to the memory moss, it acts as if affected by a confusion spell (CL 8th) for the next 1d4 hours. Lost memories can be regained by eating the memory moss that absorbed them. Doing so requires a DC 13 Fortitude save, with failure resulting in the creature being nauseated for 1d6 minutes and suffering 1d4 points of Constitution damage.
A creature that eats the memory moss temporarily gains the memories currently stored therein (even if they are not the creature’s own memories). Such creatures can even cast spells if the memory moss has stolen these from a spellcasting creature. Any non-spellcaster that attempts to cast a spell gained in this way must succeed on a concentration check (DC 10 + spell level) or the spell fizzles away. After 24 hours, the memories fade (including any spells not yet cast). Creatures eating the memory moss to regain their own lost memories do not lose them after 24 hours. Cold and fire kills a single patch of memory moss.
When first encountered there is a 25% chance that the memory moss has eaten within the last day and does not attack by stealing memories. In such a case, the moss contains 2d4 spells determined randomly (use the arcane or divine spell scroll tables). When a living creature moves within 60 feet of a sated memory moss, it assumes a vaguely humanoid form and casts the stolen spells at its targets. The moss casts these spells as a sorcerer of the minimum level necessary to cast the stolen spell (save DC 10 + spell level).
Memory Moss from the Tome of Horrors Complete, Copyright 2011, Necromancer Games, Inc., published and distributed by Frog God Games; Author Scott Greene and Erica Balsley, based on original material by Gary Gygax.