Astral Whale

Hold Breath. The whale can hold its breath for 90 minutes.

Song of the Deep. The whale knows the precise location of any creatures within 1 mile. If the whale is deafened, it loses this ability.

Keen Hearing. The whale has advantage on Wisdom (Perception) checks that rely on hearing.

Iridescent. The whale emits dim light to a range of 30 feet. 

Majestic Terror. Any creature that can see the Whale must make a DC 14 Wisdom Saving Throw at the beginning of their turn. On a failure, roll percentile dice. On a roll of 1-50, the target is charmed by the whale, and on a roll of 51-100, they are frightened. While charmed or frightened in this way, creatures are stunned, automatically fail perception checks to notice anything not directly adjacent to the whale, and are unable to look away from the whale. If a creature’s saving throw is successful or the effect ends for it, it is immune to the whale for the next 24 hours. 

Multiattack. The whale makes two attacks: one with its bite and one with its tentacles.

Bite. Melee Weapon Attack: +11 to hit, reach 5 ft., one target. Hit: 21 (3d8 + 7) piercing damage. If the target is a Large or smaller creature, it must succeed on a DC 15 Dexterity (or Intelligence if in the Astral plane) saving throw or be swallowed by the whale. A swallowed creature has total cover against attacks and other effects outside the whale, and it takes 3 (1d6) psychic damage at the start of each of the whale’s turns. If the whale takes 30 damage or more on a single turn from a creature inside it, the whale must succeed on a DC 16 Constitution saving throw at the end of that turn or regurgitate all swallowed creatures, which fall prone in a space within 10 feet of the whale. If the whale dies, a swallowed creature can escape from the corpse by using 1d6 times 5 feet of movement, exiting prone.

Tentacle. Melee Weapon Attack: +11 to hit, reach 15 ft., one target. Hit: 17 (3d6 + 7) bludgeoning damage, or 35 (6d6 + 14) bludgeoning damage if the target is an object. A target hit by this attack while underwater or in the astral plane is knocked 10 feet away.