Tendrils

Melee Weapon Attack: +9 to hit, reach 10 ft., one target. Hit: 33 (4d12 + 7) bludgeoning damage. If the target is a creature, it is grappled (escape DC 17). Until this grapple ends, the target is restrained, and the cavelight moss can't use its tendrils against another target.

Strength Drain

Living creatures hit by the cavelight moss's tendril attack or caught up in its grapple must make a successful DC 14 Constitution saving throw or 1 level of exhaustion. Creatures that succeed are immune to that particular cavelight moss's Strength Drain ability for 24 hours. For every level of exhaustion drained, the cavelight moss gains 5 temporary hit points.