Bodaks apparently date back to The Lost Caverns of Tsojcanth, but not until this year’s Undead Revisited does it seem they received serious attention (at the hands of Eric Cagle). They are created from mortals killed from exposure to absolute evil. Evil so pure is typically only to be found on the Outer Planes. PCs encountering them on the Prime Plane had best cover their eyes and pray for dawn.
The Smoking Field is an Abyssal realm where a company of paladins met its end. The gate through which they came still stands, but holy abjurations bar the now-undead paladins from returning through. Hungry for mortal souls, these bodaks stand at the edge of the spells’ boundaries, pacing back and forth like a fell crop of ashen corpses.
An artist is visited by a spirit from beyond who shows him sights of abject horror, then forces him to paint what he sees. The nightmares on his canvas eventually turn him into a bodak. Anyone attempting to lay him to rest must now also contend with a studio filled with his bodak assistants and avoid glimpsing his blasphemous final work.
A medusa necromancer seeks bodaks to study, seeing a perfection in their deadly gazes that mirrors her own.
—Pathfinder Bestiary 2 48