Inscrutable. No magic can observe the sphinx remotely or detect its thoughts without its permission. Wisdom (Insight) checks made to ascertain its intentions or sincerity are made with Disadvantage.

Legendary Resistance (3/Day, or 4/Day in Lair). If the sphinx fails a saving throw, it can choose to succeed instead.

Multiattack. The sphinx makes three Claw attacks.

Claw. Melee Attack Roll: +8, reach 5 ft. Hit: 14 (3d6 + 4) Slashing damage.

Mind-Rending Roar (Recharge 5–6). Wisdom Saving Throw: DC 16, each enemy in a 300-foot Emanation originating from the sphinx. Failure: 35 (10d6) Psychic damage, and the target has the Incapacitated condition until the start of the sphinx’s next turn.

Spellcasting. The sphinx casts one of the following spells, requiring no Material components and using Intelligence as the spellcasting ability (spell save DC 16):

At Will: Detect Magic, Identify, Mage Hand, Minor Illusion, Prestidigitation
1/Day Each: Dispel Magic, Legend Lore, Locate Object, Plane Shift, Remove Curse, Tongues

Legendary Action Uses: 3 (4 in Lair). Immediately after another creature’s turn, the sphinx can expend a use to take one of the following actions. The sphinx regains all expended uses at the start of each of its turns.

Arcane Prowl. The sphinx can teleport up to 30 feet to an unoccupied space it can see, and it makes one Claw attack.

Weight of Years. Constitution Saving Throw: DC 16, one creature the sphinx can see within 120 feet. Failure: The target gains 1 Exhaustion level. While the target has any Exhaustion levels, it appears 3d10 years older. Failure or Success: The sphinx can’t take this action again until the start of its next turn.