Agathar

Serpent Tusks. When the two serpent tusks eat it feeds the agathar.

Unpredictable Venom. When the agathar deals damage with its Serpent Bite there is a 10% chance that it does an extra 21 (4d10 + 1) poison damage.

Aggressive. As a bonus action, the agathar can move up to its speed toward a hostile creature it can see.

Charge. If the agathar moves at least 10 feet straight toward a target and then hits it with a horns attack on the same turn, the target takes an extra 17 (3d10) piercing damage. If the target is a creature, it must succeed on a DC 20 Strength saving throw or be pushed up to 10 feet away and knocked prone.

Rampage. When it reduces a creature to 0 hit points with a melee attack on its turn, the agathar can take a bonus action to move up to half its speed and make a bite attack.  

Serpent Bite (Recharge 2-3). The serpent tusks bite one target within 5 feet of the agathar.  The target must make a successful DC 15 Dexterity saving throw or take 32 (8d6 + 2) poison damage and 5 (2d4 + 1) piercing damage.  If the target fails the saving throw roll a d4 after taking the damage, a 1 or a 2 on the d4 poisons the target, and a 3 or 4 paralyzes the target.  

Horns. Melee Weapon Attack: +6 to hit, reach 6 ft., 1 target. Hit: 21 (4d6 + 8) piercing damage. 

Hooves. Melee Weapon Attack: +4 to hit, reach 2 ft., 1 target. Hit: 26 (5d6 + 8) bludgeoning damage.