Cerathrion

Legendary Resistance (5/day). If the Cerathrion fails a saving throw, it can choose to succeed instead.

Beast of Terror. The Cerathrion does double damage on attacks against frightened creatures.

Regeneration. The Cerathrion regains 50 hit points at the start of each of its turns.

Magic Attacks. The Cerathrion's attacks are magical.

Multiattack. The Cerathrion can use its Frightful Presence. It then makes six attacks: one with its slam, one with its bite, two with its claws, and two with its kick.

Mind Control. The Cerathrion attempts to take over the mind of another creature within 60 ft of it. The target must succeed on a DC 26 wisdom saving throw or follow the Cerathrion's orders for 1 minute. The Cerathrion can't convince the creature to do anything directly harmful to it or its friends, and the creature can't harm the Cerathrion unless the Cerathrion commands it to.

Deathly Gaze (Recharge 5-6). The Cerathrion gazes at creatures, rotting their souls. Each creature of the Cerathrion's choice that is within 40 ft of it must succeed on a DC 27 Constitution saving throw, taking 112 (32d6) necrotic damage on a failed save, or half as much on a successful one.

Frightful Presence. Each creature of the Cerathrion's choice that is within 120 feet of the Cerathrion and aware of it must succeed on a DC 26 Wisdom saving throw or become frightened for 1 minute. A creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success. If a creature's saving throw is successful or the effect ends for it, the creature is immune to the Cerathrion's Frightful Presence for the next 24 hours.

Bite. Melee Attack: +19 to hit, reach 10 ft., one target. Hit: 28 (4d8 + 10) piercing damage and the target must succeed on a DC 27 Constitution saving throw or take an extra 23 (5d6) poison damage and be poisoned for 1 minute. The target can repeat the saving throw at the end of each of its turns, ending the effect on a success. On a successful save the target is not poisoned and takes half the poison damage. If the target is a creature, it is grappled (escape DC 20). Until this grapple ends, the target is restrained, and the Cerathrion can’t bite another target.

Slam. Melee Weapon Attack: +19 to hit, reach 15 ft., 1 target. Hit: 48 (4d12 + 10) bludgeoning damage. 

Kick. Melee Attack: +19 to hit, reach 20 ft., 1 target. Hit: 32 (4d10 + 10) bludgeoning damage and the target is knocked prone. The Cerathrion can then make one stomp attack against the target as a bonus action.

Stomp. Melee Attack: +19 to hit, reach 10 ft., 1 target. Hit: 37 (6d8 + 10) bludgeoning damage.

Claw. Melee Attack: +19 to hit, reach 15 ft., 1 target. Hit: 23 (2d12 + 10) slashing damage and 18 (4d8) poison damage.  

Stomp.  If the Cerathrion hits a creature with a kick attack, it can use a bonus action to do an extra 37 (6d8 + 10) bludgeoning damage to the target.  

Reborn (1/day). The Cerathrion can use a bonus action to replenish all health and ability uses, provided he has at least 1 hit point. Award an additional 155,000 XP if the party defeats the Cerathrion after he uses this ability.

Alert Defense. If the Cerathrion fails a Dexterity saving throw, it can use its reaction to direct the effect to another creature it can see.

Roar. If the Cerathrion is hit with a melee weapon attack, it can use its reaction to roar, and every enemy of the Cerathrion within 120 ft. of it must succeed on a DC 26 Wisdom saving throw. On a failure, the Cerathrion has advantage on attack rolls against the creature until the end of the Cerathrion's turn. 

The Cerathrion can take 5 legendary actions, choosing from the options below. Only one legendary action option can be used at a time and only at the end of another creature's turn. The Cerathrion regains spent legendary actions at the start of its turn.

Spit (Costs 2 Actions). The Cerathrion spits acid in a 5 by 40 ft. line. Each creature in the line must make a DC 27 Dexterity saving throw, taking 52 (8d12) acid damage on a failed save.

Spellcasting (Costs 5 Actions). The Cerathrion can cast specific spells as a Titan. Those specific spells have no effect on the Cerathrion, whether he is the target or caster of the spell. Using up to three slots, the Cerathrion can cast Disintegrate at 9th level (costs 1 slot), Finger of Death (costs 1 slot), and Power Word Kill (costs 2 slots), without needing any material components (spell save DC 26). The Cerathrion regains spent spell slots at the end of each of its turns. Award an additional 50,000 XP if the party defeats him after he uses this feature.

Attack. The Cerathrion makes two kick attacks or uses its deathly gaze.

Recharge. The Cerathrion attempts to recharge one of its abilities.