Elth

Yup, it's an instakill spell, not a bug. Pretty much like the wizard's "Death ring". I guess it's the PoE equivalent of "Symbol, Death" and "Power Word: Death" from Baldur's gate series (instakill on enemies with less than 60hp)

After the recent patch, i noticed a bug with the Prone debuff from Wizard spells. As you can see on the attached screenshot, when i apply Prone on an enemy via Slicken or Call to Slumber, there is no duration on the effet. Enemies stay on the ground until killed. However, they still move, sliding on the ground chasing me, and still inflict Disengagement Attacks but don't autoattack or use spells anymore. The Prone status from enemies or my Animat invocation horn do trigger the correct debuff duration and thus end at some point, it seems to come only from my spells.