Going Mad

Various magical effects can inflict madness on an otherwise stable mind. Certain spells, such as contact other plane and symbol, can cause insanity, and you can use the madness rules here instead of the spell effects in the Player's Handbook. Diseases, poisons, and planar effects such as psychic wind or the howling winds of Pandemonium can all inflict madness. Some artifacts can also break the psyche of a character who uses or becomes attuned to them.
Resisting a madness-inducing effect usually requires a Wisdom or Charisma saving throw. If your game includes the Sanity score (see chapter 9, "Dungeon Master's Workshop"), a creature makes a Sanity saving throw instead.