Corpse-Grub

Undead Fortitude: If Corpse-Grub drops to 0 hit points, it must make a Constitution save with a DC of 5 + the damage taken, unless the damage is radiant or from a critical hit. On a success it drops to 1 hit point instead. 

Rejuvenation: If it dies, Corpse-Grub returns to life with full hit points 1d4 days later upon the consecrated ground it was created. Only a wish spell can prevent this trait from functioning. 

Multi-Attack: Corpse-Grub makes three Bash attacks. 

Bash: Melee Weapon Attack: +7 to hit, reach 5ft., one target, Hit: 9 (1d8 + 4) [bludgeoning] damage. Target must make a DC 15 Constitution saving throw or begin "bleeding," taking 3 (1d6) [piercing] damage each round for 3 rounds.