Wounding Strike (Martial Arts Maneuver)
From D&D Wiki
Don't pick a fight until you're mentally prepared to punch through your opponent.
Level: Hard 1
Type: Action (Attack)
Description: You make a wounding attack against your enemy that deals 1 point of Constitution damage. This damage is multiplied according to the critical multiplier of the weapon used when you make a critical hit. Constitution damage made through a wounding strike can be healed. For every 5 hit points restored, 1 point of Constitution damage is healed.