Bestiary unlock for Spite
Respawn timer is abt 10 minutes, so a group of 3 or 4 can take several hours.Edit
Firstly look for a Tainted Grove Spite at 9k, 61k, kill him and he will hopefully drop a BoP item called Tainted Spite Essence (it doesn't happen every time so just keep on killing him if you didn't get it) then take the item to the Bloody Sun Burner at 3000, 26000 in the Ch.3 town Komar, inside of a tent, in order to get this unlock.
(Note): Despite being a level 7 Monster, he is a Hero, and packs a pretty good punch for low armor players, so it is not advised that one tries this alone at lower levels, especially if you are a Mage or Healer class.
Following note is for the De-spite unlock not the "Defiled Life-Force" Mystical Beast unlock.
I killed Maegda (level 8) at 4k, 61k and got the unlock and the pocket item Spite Ale on turn in at the library.
If you are order do the same as above but take it to Hammerstriker Hasher beside the Krom Komar merchant.