Psi bolt

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Psi bolt[1] is a monster spell that appears in NetHack.


Psi bolt is a melee-range spell that can be used by any monster that casts mage spells. It deals damage depending on the caster's level, as with most standard calculations for monster spell damage: the damage is (ML2 + 1)d6 of damage unless the monster's casting attack specifies any dice, in which can it deals (ML2 + x)dy damage, where (x, y) is the amount and size of the damage dice.[2][3] Psi bolt's damage is halved if you have either half spell damage or magic resistance, and is reduced to 14 if you have both properties (rounded up in both cases).[4]

The higher the casting monster's level, the less likely that monster is to randomly select that spell: from levels 1 to 23, the odds decrease significantly from 100% to 4.3%. At level 24 and above, however, there is a chance that the touch of death monster spell will be replaced with a psi bolt if the player is immune to the former spell - this results in a slight bias of spell choice towards psi bolt, raising the chance to to 12% at level 25 in those cases, and raising them further to about 18% at level 50.[5]

Damage calculation shorthand

Since most monsters have either zero damage dice or 6-sided damage dice for their spellcasting attacks, the "base" damage of this spell can reliably be expressed as ml2d6 damage, with additional damage based on the monster that cast the spell: +8d6 for Orcus and Demogorgon, +6d6 for Dispater, +4d6 for Archons and golden naga, +2d6 for ki-rin and +1d6 for other monsters. Neferet the Green is the one exception, with her psi bolt dealing damage equal to (ml2 + 2)d8.


Psi bolts from high-level spellcasters can prove to be a major threat in the late game. Though the touch of death is more immediately run-threatening, a strong enough psi bolt can still deal significant damage through magic resistance that would nullify the former spell completely.


In NetHack 3.3.1 and earlier versions, including some various based on those versions, magic resistance reduced damage from the attack to 1, according to a comment in the code.

In NetHack 3.4.3 and earlier versions, including some various based on those versions, the relative frequency of the psi bolt spell would rapidly increase starting at level 24, passing 50% at level 44.[6] Spellcasting monsters with a very high level would use this spell very often, which could be a high-damage hazard to a player character (e.g. 33d6 base damage for a psi bolt from Demogorgon).


Message Damage dealt
"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+



In SLASH'EM, there are many new monsters that can cast mage spells - using the shorthand methods described above, the additional damage values are as follows: +6d6 for ghoul mages, +5d6 for Solars, +4d6 for Planetars and ghoul queens, +2d6 for vampire mages, and +1d6 for all others.

As SLASH'EM is a 3.4.3 variant, high-level spellcasters are very likely to cast psi bolt - this includes Demogorgon and Dispater, who are guaranteed encounters alongside the other demon lords and princes that are optional in vanilla NetHack.