Behemoth

Divine Being. The behemoth can't be surprised and can't be changed into another form against its will.

Energy Absorption. When the behemoth is subjected to necrotic or radiant damage, it takes no damage and instead regains a number of hit points equal to the damage dealt.

Legendary Resistance (3/Day). If the behemoth fails a saving throw, it can choose to succeed instead.

Magic Weapons. The behemoth's weapon attacks are magical.

Siege Monster. The behemoth deals double damage to objects and structures.

Spell-Resistant Scales. The behemoth has advantage on saving throws against spells and other magical effects, and any creature that makes a spell attack against the behemoth has disadvantage on the attack roll.

Unusual Nature. The behemoth doesn't require air, food, drink, or sleep.

Multiattack. The behemoth makes one Bite attack, two Claw attacks, and one Tail attack.

Bite. Melee Weapon Attack: +18 to hit, reach 15 ft., one target. Hit: 36 (4d12 + 10) piercing damage. If the target is a Large or smaller creature, it must succeed on a DC 26 Dexterity saving throw or be swallowed by the behemoth. While swallowed, the creature is blinded and restrained, it has total cover against attacks and other effects outside the behemoth, and it takes 56 (16d6) acid damage at the start of each of the behemoth’s turns.

If the behemoth takes 50 damage or more on a single turn from a creature inside it, the behemoth must succeed on a DC 28 Constitution saving throw at the end of that turn or regurgitate all swallowed creatures, which fall prone in a space within 10 feet of the behemoth. If the behemoth dies, a swallowed creature is no longer restrained by it and can escape from the corpse by using 30 feet of movement, exiting prone.

Claw. Melee Weapon Attack: +18 to hit, reach 15 ft., one target. Hit: 32 (4d10 + 10) slashing damage.

Tail. Melee Weapon Attack: +18 to hit, reach 15 ft., one target. Hit: 28 (4d8 + 10) bludgeoning damage.

Energy Breath (Recharge 5-6). The behemoth exhales energy in a 300-foot line that is 10 feet wide. Each creature in the area must succeed on a DC 26 Dexterity saving throw, taking 72 (16d8) necrotic or radiant damage (behemoth’s choice) on a failed save, or half as much damage on a successful one. Creatures reduced to 0 hit points by this damage dies and are obliterated, leaving behind no trace of the creature. The behemoth’s Energy Breath destroys objects that aren’t being worn or carried and barriers of magical force in the area, such as a wall of force spell.

Teleport. The behemoth teleports, along with any equipment it is wearing or carrying, up to 120 feet to an unoccupied space it can see.

The behemoth can take 3 legendary actions, choosing from the options below. Only one legendary action can be used at a time and only at the end of another creature's turn. The behemoth regains spent legendary actions at the start of its turn.

Attack. The behemoth makes one Claw or Tail attack.

Earthshaking Stomp. The behemoth strikes the ground with a mighty stomp, causing an earthquake to affect the ground in a 100-foot-radius circle centered on the behemoth. Each creature in contact with the ground, other than the behemoth, must succeed on a DC 26 Strength saving throw or be knocked prone. The earthquake might have additional effects depending on the terrain in the area, similarly to an earthquake spell.

Teleport. The behemoth uses Teleport.

Devour (Costs 2 Actions). The behemoth makes one Bite attack with advantage.