Manabane Scarab Swarm

Swarm. The swarm can occupy another creature's space and vice versa, and the swarm can move through any opening large enough for a Tiny insect. The swarm can't regain hit points or gain temporary hit points.

Magic Immunity. The manabane scarab swarm is immune to spells and other magical effects.

Scent Magic. The manabane scarab swarm can detect the presence of magical creatures, active spells or spell effects, and magical items within 120 feet.

Mana Erosion. The manabane scarab swarm consumes magic. Unattended magic items in the swarm's space at the end of the swarm's turn have their effects suppressed for 1 minute. Additionally, charged items in the swarm's space lose 1d6 charges at the start of each of the swarm's turns; items with limited uses per day lose one daily use instead, and single-use items such as potions or scrolls are destroyed. Magical effects in the swarm's space are dispelled (as if affected by dispel magic cast with +5 spellcasting ability).

Bites. Melee Weapon Attack: +5 to hit, reach 0 ft., one creature in the swarm's space. Hit: 14 (4d6) piercing damage, or 7 (2d6) piercing damage if the swarm has half of its hit points or fewer. The target must succeed on a DC 15 Dexterity saving throw or one randomly determined magic item in its possession is immediately affected by the Mana Erosion trait. A spellcaster hit by this attack must succeed on a DC 15 Charisma saving throw or one of its lowest-level, unused spell slots is expended.