Sigbin

It walks backwards with its head lowered between its hind legs, which is a difficult thing to picture and a much worse thing to see coming. The sigbin does not go for the body. It goes for the shadow, and whatever it does to the shadow happens to the person casting it, at a distance, without being touched. Keeping out of the light does not help. It is patient and there is always light eventually.

Take the Shadow: 30 ft, requires the target to be casting a shadow. No attack roll and no line of effect to the body is needed - only to the shadow. Save Con Tough, fail save roll 1d6+2 necrotic. Cooldown 2 rounds. Bite: piercing, melee 5 ft, +2 to hit, 1d6+2, used reluctantly and at close quarters only.

Backward: it approaches rear-first with its head low and is extremely hard to read. It cannot be flanked, and any creature attacking it for the first time does so at disadvantage. No Shadow, No Attack: a creature in full darkness, in fog, or standing in another's shadow cannot be targeted by Take the Shadow at all. Dousing the lights is the answer and it costs you seeing the sigbin.