Cranium Burster Scorpion

Implantation: If the scorpion’s sting attack reduces a grappled creature to 0 hit points, or it bites a target that’s already at 0 hit points, it implants an egg in the creature’s skull through their eye socket.

The deposited egg grows for 2 tenday before hatching. If the implanted target is still alive, it loses 1 Constitution every day and has disadvantage on attack rolls and ability checks. After the first tenday, the victim is incapacitated and blinded.

When the egg hatches, an young scorpion (half all dmg and hp) erupts from the victims head, causing 3d10 slashing damage. A lesser restoration spell can kill the egg during its incubation.

Additionally, ingesting certain poisons can kill the egg before it hatches, but at horrible risk to the victim.

Multiattack. The scorpion makes three attacks: two with its claws and one with its sting.

Claw. Melee Weapon Attack: +4 to hit, reach 5 ft., one target. Hit: 6 (1d8 + 2) bludgeoning damage, and the target is grappled (escape DC 12). The scorpion has two claws, each of which can grapple only one target.

Sting. Melee Weapon Attack: +4 to hit, reach 5 ft., one creature. Hit: 7 (1d10 + 2) piercing damage, and the target must make a DC 12 Constitution saving throw, taking 22 (4d10) poison damage on a failed save, or half as much damage on a successful one.