Rigor Mortis

Rigor Mortis is a  passive skill, unlocked at level 27.

In-game
This skill applies to all damaging skills that have a Poison rune, but not to other sources of Poison damage.

Trivia

 * Rigor mortis (Latin: rigor "stiffness", mortis "of death") is the third stage of death, one of the recognizable signs of death, caused by chemical changes in the muscles post mortem, which cause the limbs of the corpse to stiffen.