Asphyxiation

Asphyxiation is an extremely rare form of damage caused by your character's sudden and painful inability to breathe. There are two sources:

• Anyone struck by curare needles will take 2d6 points of asphyxiation damage, along with becoming poisoned and slowed, unless they have poison or asphyxiation resistance.
• Anyone struck by the Primal Wave spell will take heavy, partially irresistible asphyxiation damage. Amphibious species (merfolk and octopodes) and characters with asphyxiation resistance take 40% less damage than normal.

You can only acquire asphyxiation resistance by playing a mummy or a grey draconian (the two species that don't actually breathe).