Multiattack

If the chuul is grappling a creature it uses its tentacle on that creature. It then makes two pincer attacks.

Pincer

Melee Weapon Attack: +7 to hit, reach 5 ft., one Large or smaller target. Hit: 11 (2d6 + 4) bludgeoning damage. If the target is a creature it is grappled (escape DC 15). When carrying a grappled creature the chuul can move at full speed. A pincer that is being used to grapple a creature can be used only to attack that creature.

Tentacle

A grappled creature makes a DC 14 Constitution saving throw. On a failure it is paralyzed for 1 minute. The creature repeats the saving throw at the end of each of its turns ending the paralysis on a success.