The Pain domain was a deity domain that granted divine spellcasters like clerics with spells and powers themed around pain.
Cyric • Loviatar
A cleric with the Pain domain could convert an injury dealt from one blow into healing for him or herself, once a day.
Novice spellcasters were able to use the angry ache, sadism, and wrack spells. Clerics of some experience could cast liquid pain, thousand needles, and pox. Those that were masters of this domain had access to wave of pain, symbol of pain, and eternity of torture.
The Pain domain originated in the Book of Vile Darkness, and was added to the Forgotten Realms setting by the Player's Guide to Faerûn.
3rd, 3.5, and 5th Editions