Tenacious is one of the traits in Guild Of Dungeoneering.
Description[ | ]
Death is only possible if hit while at 1 HP
Any hit that would normally result in defeat when at 2+ HP will instead set HP to 1, and Tenacious will be disabled for the next round. If able to heal to 2+ HP after this, Tenacious will activate again (i.e., it works every time HP is greater than 1, not just once per battle).