Behir

Huge monstrosity, neutral evil

Armor Class 17 (natural armor)

Hit Points 168 (16d12+64)

Speed 50ft., climb 40ft.

Skills Perception +6, Stealth +7

Damage Immunities lightning

Senses darkvision 90ft., passive Perception 16

Languages Draconic

Challenge 11 (7,200 XP)

Actions

Multiattack

The behir makes two attacks: one with its bite and one to constrict.

Bite

Melee Weapon Attack: +10 to hit, reach 10ft., one target.
Hit: 22 (3d10+6) piercing damage.

Constrict

Melee Weapon Attack: +10 to hit, reach 5ft., one Large or smaller creature.
Hit: 17 (2d10+6) bludgeoning damage plus 17 (2d10+6) slashing damage. The target is grappled (escape DC 16) if the behir isn't already constricting a creature, and the target is restrained until this grapple ends.

Lightning Breath (Recharge 5-6)

The behir exhales a line of lightning that is 20ft long and 5ft wide. Each creature in that line must make a DC 16 Dexterity saving throw, taking 66 (12d10) lightning damage on a failed save, or half as much damage on a successful one.

Swallow

The behir makes one bite attack against a Medium or smaller target it is grappling. If the attack hits, the target is also swallowed, and the grapple ends. While swallowed, the target is blinded and restrained, it has total cover against attacks and other effects outside the behir, and it takes 21 (6d6) acid damage at the start of each of the behir's turns. A behir can have only one creature swallowed at a time.

If the behir takes 30 damage or more on a single turn from the swallowed creature, the behir must succeed on a DC 14 Constitution saving throw at the end of that turn or regurgitate the creature, which falls prone in a space within 10ft of the behir. If the behir dies, a swallowed creature is no longer restrained by it and can escape from the corpse by using 15ft of movement, exiting prone.