When you are at less than 5 hp, a swarm of 5 dark mantles will come to your aid. You are able to control them and decide who they attack or defend. If you do choose, you don’t even need to tell them what to do, and put that responsibility on the dm. They are friendly to you and your party, and if you take any damage, they will make a Dc 14 dexterity saving throw to try and take the damage for you, like the pig in gungeon. This whole feat is basically a copy of the ‘faithful summons’ ability for druids, but available to anyone.