Its the Necrolord Demon Hunter covenant ability, killing the Demon (glaive throw insta kills it iirc) gets you a demon soul that boosts dps for a short time iirc.
Yeah, my DH is necrolord as well (I don’t know if it’s good or not, just wanted a character in each covenant), and it’s mildly annoying when you are farming legacy stuff, one shotting everything, and you stay in combat because of the demon that spawns.
A tip to the OP. The demon dies instantly if you use the Thwor Glaive ability on it.
no, i did not read the full tooltip, just missed a button to press for my ability, when there was none (i thought), i became glad. even less buttons to press for this class with so many