Aberrant Ground. The ground in a 10-foot radius around the blister is difficult terrain, covered in tangled knots of oozing tendrils. Each creature that starts its turn in that area must succeed on a DC 10 Strength saving throw or have its speed reduced to 0 until the start of its next turn.

Multiattack. The blister makes 1d4 Necrotic Lash attacks.

Necrotic Lash. Melee Weapon Attack: +2 to hit, reach 10 ft., one creature. Hit: 4 (1d8) necrotic damage.

Blister Burst. The blister self destructs by bursting open and splashing necrotizing ooze in a 15 foot radius. All creatures within range must make a DC 13 Dexterity Saving Throw or take 11 (2d10) necrotic damage. The blister drops to 0 hit points when it completes this action and cannot be healed.