Astel, Naturalborn of the Void

Legendary Resistance (3/Day). If Astel fails a saving throw, it can choose to succeed instead.

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

Multiattack. Astel can use its Frightful Presence or its teleport. It then makes three attacks: one with its bite and two with its claws. Astel can substitute his bite attack for a grab or teleporting grab.

Pincer Bite. Melee Weapon Attack: +14 to hit, reach 10 ft., one target. Hit: 19 (2d10 + 8) piercing damage plus 7 (2d6) necrotic damage.

Claw. Melee Weapon Attack: +14 to hit, reach 5 ft., one target. Hit: 15 (2d6 + 8) slashing damage.

Tail. Melee Weapon Attack: +14 to hit, reach 15 ft., one target. Hit: 17 (2d8 + 8) bludgeoning damage.

Frightful Presence. Each creature of Astel's choice that is within 120 feet of Astel and aware of it must succeed on a DC 19 Wisdom saving throw or become frightened for 1 minute. A creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success. If a creature's saving throw is successful or the effect ends for it, the creature is immune to Astel's Frightful Presence for the next 24 hours.

Teleport. Astel instantly teleports up to 100 feet, or anywhere within his lair.

Teleporting Grab. Astel immediately teleports up to 100 feet and attempts to grapple his target with his pincers. Astel can then choose to throw that target up to 40 feet as one of his attacks, dealing 6d8 bludgeoning damage.

Waves of Darkness(Recharge 5-6). Astel slams the ground with his hands sending out waves of necrotic energy. The first wave strikes everything within 20 feet. The second travels 40 feet. The third travels 60 feet. This attack can hit the same target multiple times. Each wave does 2d8 necrotic damage or half as much on a successful DC 17 Constitution saving throw.

Cosmic Burst(Recharge 5–6). Astel exhales necrotic energy in a 100-foot line. Each creature in that area must make a DC 21 Dexterity saving throw, taking 63 (18d6) necrotic damage on a failed save, or half as much damage on a successful one.

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.

Detect. Astel makes a Wisdom (Perception) check.

Tail Attack. Astel makes a tail attack.

Wing Attack (Costs 2 Actions). Astel beats its tattered wings. Each creature within 10 feet of Astel must succeed on a DC 22 Dexterity saving throw or take 15 (2d6 + 8) bludgeoning damage and be knocked prone. Astel can then fly up to half its flying speed.