Psi bolt is the internal name for the weakest of the monster spells (though it is never referred to in the game as such) and as such can be cast by any spell-casting monster. It will deal an amount of damage equivalent to (half the monster's level)d6, which can be halved by possessing a "half spell damage" artifact (e.g. the Eye of the Aethiopica).
|"You get a slight <head>ache."||0-5|
|"Your brain is on fire!" (not to be confused with intelligence drain)||6-10|
|"Your <head> suddenly aches painfully!"||11-20|
|"Your <head> suddenly aches very painfully!"||21+|