Swarm Body. You can occupy another creature's space and vice versa, and you can move through any opening large enough for a Tiny beast.

Thrash. You can use a bonus action to expend one spell slot to force each creature of your choice within 5 feet of you to make a Dexterity saving throw against your druid spell save DC, taking bludgeoning, piercing, poison, or slashing damage equal to 1d8 per level of the spell slot expended + PB on a failed save. You choose the type of damage dealt by this trait each time you enter this form.

Mob. Melee Weapon Attack: +5 to hit, reach 5 ft., one target in the swarm's space. Hit: Damage equal to 1d10 + PB + your druid level. The type of damage is the same type that your Thrash trait deals.