Vorren, the Eldest

Confusion Aura. A creature within 30 feet of the Eldest must make a DC 27 Wisdom saving throw. On a failure, the target is under the effects of the confusion spell until the end of its next turn. On a success, the target is immune to the effects of this aura for 24 hours.

Adamantine Shell. Critical hits against the Eldest count as normal, non-critical hits.

Legendary Resistance (5/day). If the Eldest fails a saving throw, it can choose to succeed instead.

Magic Weapons. The Eldest's weapon attacks are magical.

Fulcrum Anchor. The Eldest cannot be banished or teleported away from its current location. Additionally, no teleportation or plane-shifting is possible within a 120 ft. radius of it without consent.

Innate Spellcasting. The Eldest's innate spellcasting ability is Charisma (spell save DC 27, +19 to hit with spell attacks). It can innately cast the following spells, requiring no material components:

At will: blur, confusion, dimension door, dispel magic (at 5th level), haste, invisibility, lightning bolt, mage armor, magic missile, shield, stoneskin, true strike, web

3/day each: chain lightning, cone of cold, disintegrate, dominate person, plane shift, prismatic spray, scrying, teleport, wall of force

1/day each: time stop

Strike. Unarmed Weapon Attack: +17 to hit, reach 10 ft., one creature. Hit: 43 (10d6+8) piercing damage. The target must make a DC 27 Constitution saving throw. On a failure, the target's Constitution score is reduced by 1d4 and the Eldest regains 5 hit points. The target dies if this reduces its Constitution to 0 and cannot be resurrected.

When attacked, the Eldest casts shield as a reaction.

The Eldest can take 5 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. The monster regains spent legendary actions at the start of its turn.

Strike. The Eldest makes one strike attack.

Cast a Spell (2 actions). The Eldest casts a spell from its spell list (excluding contingent resurrection, nailed to the sky, time duplicate, and time stop).