Once an Immortal Skeleton's health is reduced to nothing, it will collapse to the ground revealing a blue mystic sword protruding from its back. The sword yields a prompt to Pull using the action button. If it is not removed within seconds the Immortal Skeletaur will rise up again and resume the fight at full health, and will have gained one level. Pulling the sword free ends the curse sustaining the skeleton and destroys it.
As the sword always presents the "Pull" prompt to a character directly facing it, it is possible to quickly dispatch an Immortal Skeletaur before its health is depleted. Additionally, the skeleton has a slow recovery period after performing a lunge attack, which if evaded leaves brief delay to outflank and pull the sword early.
- In TVH Mode they are renamed Relentless Skeletaur, and in UVH Mode they are renamed Eternal Skeletaur.
- Experience for destroying an Immortal Skeletaur is not awarded until the sword is pulled free.
- Killing an Immortal Skeletaur counts towards the "Bone Breaker" challenge in the challenge list.
- Immortal Skeletaurs cannot be used for getting a second wind by a downed character, because a downed character cannot be used to withdraw the sword.
- They can level up to 50 in normal, 65 in True Vault Hunter Mode, 89 on Ultimate Vault Hunter Mode, and 97 in OP8.
- Immortal Skeletaurs cannot be held by Phaselock, but instead will take damage from the force of the phaselock and its supplementary damage skills if applicable.
- Immortal Skeletaurs are defined in-game as badasses, and so characters may shout related quotes when they appear.