Sacrifice

 allows a Sentinel to revives its owner at the cost of its own life.

Acquisition
For a short time after Update 10.6 this mod could have been acquired via Transmutation. This was due to a bug where all mods, including unreleased ones such as this one, became obtainable through transmutation. This has since been fixed, but players who obtained the mod this way were allowed to keep them. There is currently no way to obtain this mod.