Thripper

Feybane Weapons. Its weapons are cold iron and are magical when used vs. fey. When it hits a fey with any weapon the weapon's damage is force instead of its normal damage type.

Fey Sense. Can pinpoint by scent the location of fey within 60' of it and can sense the general direction of fey within 1 mile of it.

Soft Wings. Can fly up to 40' on its turn but must start and end its move on solid surface (roof ground etc.). If it is flying at the end of its turn it falls to the ground and takes falling damage.

Multiattack. Two Extractor Spear or Disorienting Chitter attacks.

Extractor Spear. Melee Weapon Attack: +7 to hit, 10 ft., one target, 13 (2d8+4) piercing damage + 7 (2d6) necrotic. Target's hp max is reduced by amount equal to half necrotic taken and thripper regains hp equal to that amount. Reduction lasts until target finishes short/long rest. Target dies if this reduces its hp max to 0.

Disorienting Chitter. Ranged Spell Attack: +6 to hit, 60 ft., one target, 16 (3d8+3) thunder and the target must make DC 14 Wis save or fall prone as it briefly becomes disoriented and falls.

Glamour Counter. When creature thripper can see within 30' of it casts spell can counter the spell. This works like counterspell spell with +6 spellcasting ability check except thripper can counter only enchantment or illusion spells and it must make the ability check regardless of spell's level.