Actions

Multiattack. The behemoth makes one Strike and one Stomp attack.   Strike. Melee Weapon Attack: +17 to hit, reach 15 ft., one target. HitL 28 ( 4d8+10 ) bludgeoning, piercing, or slashing damage (your choice). The behemoth can choose to halve the attack's damage to also grapple the target (escape DC 19), provided it is Huge or smaller. A target grappled this way is also restrained. Only one creature can be grappled this way at a time.   Stomp. Melee Weapon Attack: +17 to hit, reach 10 ft., one target. Hit: 23 ( 2d12+10 ) bludgeoning damage. Hit or miss, all other creatures within 10 feet of the target must make a DC 19 Dexterity saving throw, taking 2d12 bludgeoning damage on a failed save, or half as much on a successful one. Additionally, structures in that area automatically take the damage.   Swipe. Melee Weapon Attack: +17 to hit, reach 20 ft., one target. Hit: 19 ( 2d8+10 ) bludgeoning damage. Until the start of its next turn, attacks against the behemoth do not benefit from flanking bonuses.   Burst (Recharge 6). The behemoth sends out a burst of acid, frost, fire, shrapnel, or thunder in a 60-foot cone. Creatures in that area must make a DC 19 Dexterity saving throw. On a failed save, a creature takes 5d8 acid, cold, fire, piercing, or thunder damage (choose one when you create the behemoth). A creature takes half as much damage on a successful save. Depending on the damage you choose, additional effects occur as below.

• Acid. The damage dice become d4s but there are twice as many. Structures and objects in the area that aren't being worn or carried take the burst's damage.
• Cold. A creature that fails its saving throw has its speed halved until the start of the behemoth's next turn. If the creature failed by 10 or more, it is restrained for that duration. Also, nonmagical liquids in the area freeze.
• Fire. The damage increases by 1d8. Also, objects in the area that aren't being worn or carried ignite.
• Piercing. The damage dice become d4s but there are twice as many. A creature that fails the saving throw by 10 or more takes an additional 5d4 damage.
• Thunder. A creature that fails its saving throw is pushed 10 feet away from the behemoth, deafened until the start of the behemoth's next turn, and knocked prone.