The yann-an-oed emits an owl-like hoot from a blowhole near the top of its head. Each creature within 120 feet that is able to hear the sound must succeed on a DC 12 Wisdom saving throw or return the hooting sound, if it can make noise. The yann-an-oed is able to unerringly track a creature that responds to its call for 1 hour, even if the creature is hidden by magic or on another plane of existence.

The yann-an-oed makes a bite attack against a Large or smaller creature 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 yann-an-oed, and it takes 7 (2d6) acid damage at the start of each of the yann-an-oed’s turns. A yannan-oed can have only one creature swallowed at a time. If the yann-an-oed takes 10 damage or more on a single turn from the swallowed creature, the yann-an-oed must succeed on a DC 11 Constitution saving throw at the end of that turn or regurgitate the creature, which falls prone in a space within 10 feet of the yann-an-oed. If the yann-an-oed dies, a swallowed creature is no longer restrained by it and can escape from the corpse by using 10 feet of movement, exiting prone.