Limited Spell Immunity. The swarm automatically succeeds on saving throws against spells of 3rd level or lower, and the attack rolls of such spells always miss it.
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 gremishka. The swarm can't regain hit points or gain temporary hit points.
Bites. Melee Weapon Attack: +4 to hit, reach 0 ft., one target in the swarm's space. Hit:12 (3d6 + 2) piercing damage, or 5 (1d6 + 2) piercing damage if the swarm has half of its hit points or fewer, plus 7 (2d6) force damage.
Spell Redirection. In response to a spell attack roll missing the swarm, the swarm causes that spell to hit another creature of its choice within 30 feet of it that it can see.
Gremishkas are the vicious products of mistakes made by novice spellcasters seeking to create life. The results are cat-sized, magically unstable creatures with a taste for the trappings of magic—particularly spellbooks, spell components, familiars, and the like. Gremishkas delight in tormenting magic-users, holding vicious grudges against those who gave them life as they infest the walls of spellcasters' homes or the surrounding lands.