Armored skeletal two-headed crocodile

• Its AC is 14
• Its tail attack does slashing damage
• It does not have a vulnerability to bludgeoning damage
• It is treated as having metal armor for the purposes of spells such as heat metal and shocking grasp.

Aquatic ambush predator. When in the water, this creature has Stealth expertise and advantage on Stealth checks.

Tetanus-bearer. Any creature that suffers damage from the attacks of this creature needs to make a DC10 constitution saving throw or contract tetanus.

• Tetanus. Incubation period 1 day. Disadvantage on Dexertity-baaed rolls after 1 day, total paralysis after 4 days, death check every day after the 7th day

Two-Headed. The armored skeletal two-headed crocodile has advantage on Wisdom (Perception) checks and on saving throws against being blinded, charmed, deafened, frightened, stunned, and knocked unconscious.

Multiattack. The armored skeletal two-headed crocodile makes two attacks with its bite and one tail attack.

Bite. Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit: 8 (1d8 + 3) piercing damage, and the target is grappled (escape DC 13). Until this grapple ends, the target is restrained, and that head of the crocodile can't bite another target.

Shake a grappled target. Automatic hit, reach 0ft, one target. Hit: 8 (1d8 + 3)  slashing damage. So long as the creature has something grappled in its jaws, it can choose to shake it, automatically inflicting damage.

Tail slash. Melee Weapon Attack: +5 to hit, reach 10 ft., one target not grappled by the crocodile. Hit: 12 (2d8 +3) slashing damage. If the target is a creature, it must succeed on a DC 16 Strength saving throw or be knocked prone.