Amphibious. The Black Guard Drake can breathe air and water.

Regenerates 10 health around unless hit by radiant damage

Undead Fortitude. If damage reduces the zombie to 0 hit points, it must make a Constitution saving throw with a DC of 5 + the damage taken, unless the damage is radiant or from a critical hit. On a success, the zombie drops to 1 hit point instead

Multiattack. The guard drake makes two attacks: one with its bite and one with its tail.

Bite. Melee Weapon Attack: [rollable]+5 to hit, reach 5 ft., one target. Hit: 7 1d8+3"

Tail. Melee Weapon Attack: +5 hit" reach 5 ft. (1d6 + 3);