Apophis

Apophis is a large, deep red snake that towers about 10 feet in the air at full height, stretching at a full length of 16 feet long. Blood-like poison drips from his fangs, and his eyes are solid black like the depths of the lower planes which he slithered out from.

Bite. Melee Weapon Attack: +6 to hit, reach 10 ft., one target. Hit: 9 (2d4 + 4) piercing damage, and the target must make a DC 11 Constitution saving throw, taking 14 (4d6) poison damage on a failed save, or half as much damage on a successful one.

Poison Spray. Apophis spits out a red, poisonous spray in a 30-foot cone. Each creature in that area must make a DC 13 Constitution saving throw or be poisoned for 1 minute.

Tail Snap. If Apophis is hit with a melee weapon or spell attack, he may use his reaction to snap his tail at the attacker. Target must succeed on a DC 14 Dexterity saving throw or get pushed back 20 ft. and is stunned for one round.