Astel, Naturalborn of the Void

Legendary Resistance (3/day). If Astel would fail a saving throw, it can instead choose to succeed.

Magic Resistance. Astel has advantage on saving throws against spells and other magical effects.

Multiattack. Astel uses its Teleport action, and then makes up to two with its bite and one with its tail. Astel can replace both of its bite attacks with a use of its Cosmic Burst attack.

Teleport. Astel summons a glowing orb above itself, before teleporting to a space it is aware of within 120ft. All creatures within 5ft of the space Astel left must succeed on a DC 21 Constitution saving throw, or take 9 (2d8) psychic damage.

Bite. Melee Weapon Attack: +14 to hit, reach 5 ft., one target. Hit: 21 (4d6 + 7) piercing damage.

Tail. Melee Weapon Attack: +14 to hit, reach 60 ft., one creature. Hit: 29 (4d10 + 7) bludgeoning damage.

Cosmic Burst. Astel fires a massive blast of violet magic from its mouth in a 120ft long line that is 5ft wide. All creatures within the area must make a DC 21 Dexterity saving throw. On a failed save, they take 36 (8d8) psychic damage, or half as much on a successful one.

Reverse Gravity. Astel casts Reverse Gravity, centred on itself but it is unaffected by the spell. The spell ends at the start of Astel's next turn.

Astel can take 3 legendary actions, choosing from the options below. Only one legendary action option can be used at a time and only at the end of another creature’s turn. Astel regains spent legendary actions at the start of its turn.

Tail Slam. Astel makes a Tail attack.

Nebula (Costs 2 actions). Astel sweeps a hand in front of itself, forming a cloud of stardust in a 15ft cone in front of itself that then explodes. All creatures within the cloud must make a DC 21 Strength saving throw. On a failed save, they take 27 (6d8) psychic damage and are knocked prone, or half as much on a successful one and are not knocked prone.

Diving Grab (Costs 2 actions). Astel uses its Teleport action, landing on top of a target of its choice within range. The target must succeed on a DC 21 Dexterity saving throw, or they are grabbed by Astel and shoved into its mouth, where it then chomps down on them, dealing 35 (8d6+7) piercing damage. Astel then throws the target up to 30ft away, where they land prone.