Charge. If the udaak moves at least 20 feet straight toward a target and then hits it with a slam attack on the same turn, the target takes an extra 27 (6d8) bludgeoning damage. If the target is a creature, it must succeed on a DC 21 Strength saving throw or be pushed up to 20 feet away from the udaak and knocked prone.

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

Many Limbed. The udaak can grapple up to five creatures: one with each of its arms, and one with its mouth.

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

Multiattack. The udaak can use its Primal Scatter. It then makes three attacks: one with its bite and two with its slam.

Primal Scatter. Each creature of the udaak's choice that it is grappling is flung away from it. A creature can attempt a DC 21 Strength saving throw to hold on to the Udaak and not be thrown. Otherwise, it is flung 40 feet away from the udaak in a direction of the udaak's choice, it takes 27 (6d8) bludgeoning damage, and it is knocked prone.

Bite. Melee Weapon Attack: +15 to hit, reach 5 ft., one creature. Hit: 21 (2d12 + 8) piercing damage, and the target is grappled (escape DC 21). Until this grapple ends, the target is restrained, and the udaak can’t bite another target.

Slam. Melee Weapon Attack: +15 to hit, reach 10 ft., one target. Hit: 21 (3d8 + 8) bludgeoning damage.

Primal Leap. The udaak leaps 60 feet in any direction, including up. It takes no damage from falling, unless it lands on a lower surface than the surface it leaped from, in which case that height difference is used to calculate the height of the fall.

The udaak can take 3 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 udaak regains spent legendary actions at the start of its turn.

Snatch. The udaak moves up to half its movement speed. Then, one creature of the udaak's choice within 10 feet of it must make a DC 21 Strength or Dexterity saving throw (the creature may choose which). If it fails, it is grappled by the udaak.

Swallow (Costs 2 Actions). The udaak makes one bite attack against a Large or smaller target that is restrained and which it is grappling. If the attack hits, the target is also swallowed, and the grapple ends. A swallowed creature is blinded and restrained, it has total cover against attacks and other effects outside the udaak, and it takes 21 (6d6) acid damage at the start of each of the udaak’s turns.

If the udaak takes 30 damage or more on a single turn from a creature inside it, the udaak must succeed on a DC 21 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 udaak. If the udaak dies, a swallowed creature is no longer restrained by it and can escape from the corpse by using 20 feet of movement, exiting prone.