Sphinx of Lore

A sphinx of lore on the party's side is a one-scene ally with a riddle attached. It is a Lawful Neutral CR 11 Celestial that guards knowledge, not people, so it helps because helping serves the truth, not because it likes the party. Truesight 120 ft., Inscrutable (Wis Insight checks against it have disadvantage), and Intelligence 18 with Arcana, History, and Religion all at +12 mean the sphinx is the most informed NPC the party will ever meet. Use the alliance to deliver one specific piece of forbidden lore the party could not have learned any other way.

The price of the alliance is the sphinx's terms. It will answer one question per favor, in riddle form, and the party has to interpret it correctly. It will cast Legend Lore on a named subject (1 per day) or Locate Object (1 per day) on a relic the party describes. Plane Shift (1 per day) can move the party between planes once per arc. These are quest-defining utilities, not combat helpers, and the sphinx will not waste them on logistics.

If a fight breaks out around the alliance, the sphinx joins on its own initiative roll of 20 (initiative mod +10) and will absolutely overshadow the party. Open with Mind-Rending Roar in a 300 ft. emanation: every enemy makes a DC 16 Wisdom save or takes 35 psychic and is Incapacitated until the start of the sphinx's next turn. Half on a save is still 17. After the roar, three Claw attacks at +8 for 14 slashing each, with Arcane Prowl as a legendary action to teleport 30 ft. and add another claw. Save Weight of Years for the enemy commander; one failed DC 16 Con save is one Exhaustion level and the target visibly ages 3d10 years. Dispel Magic and Remove Curse are saved for the party's actual quest needs, not for combat.

The sphinx leaves the moment the favor concludes. It does not linger or chat, and it will not rescue the party from a follow-up fight. The exit is the entire point of meeting it.

Write the riddle on a card the night before the session. Riddles improvised at the table are always too easy or too obscure, never both at once.

A hostile sphinx of lore is a knowledge-protection scene gone wrong. The setup is that the party has tried to take, copy, or destroy something the sphinx is sworn to guard, or has answered a riddle wrongly and refused to leave. Sphinxes do not stalk parties; they wait. The fight happens in the sphinx's library, vault, or planar pocket, and it happens because the party would not back down.

The opener is Mind-Rending Roar from the sphinx's first turn if recharge allows. DC 16 Wisdom save in a 300 ft. emanation, 35 psychic on fail, Incapacitated until the start of its next turn. A clustered party loses one casting round and most of a second to that single ability. After the roar, three Claw attacks at +8 for 14 slashing each, and Multiattack will absolutely target the wizard who tried to read the forbidden book.

Legendary actions structure the encounter. Arcane Prowl teleports the sphinx 30 ft. and lands a Claw, which means there is no safe range; the sphinx can reach the party's back line in a single legendary action. Weight of Years on the paladin or fighter (DC 16 Con save) is an Exhaustion level and a visible 3d10 years of age, which is its own narrative weight. Burn Legendary Resistance (3 per day, 4 in lair) on Banishment, Hold Monster, or any save that ends the fight. Truesight 120 ft. and Inscrutable mean the rogue's Greater Invisibility and the bard's Suggestion both bounce. Magic Resistance is not on this stat block; do not invoke it.

The sphinx will accept surrender at any point. It is Lawful Neutral, not Lawful Evil. If the party drops weapons and offers to leave the lore behind, the sphinx stops attacking and lets them walk, with the warning that next time it will not. If they refuse, it goes for the kill with calm efficiency.

Speak only in formal Celestial-tinted Common, with no contractions. The voice should feel older than the campaign.