Androsphinx

An androsphinx bears the head of a humanoid male on its lion's body. Outwardly gruff and downcast, it often begins conversations with insults or negative observations. Beneath this gruff exterior, however, an androsphinx has a noble heart. It has no wish to lie or deceive, but it doesn't give away information readily, choosing its words as wisely as it guards its secrets.
An androsphinx tests the courage and valor of supplicants, not only by forcing them to complete quests but also with its terrible roar, which echoes for miles as it terrifies and deafens nearby creatures. Those who pass its tests may be rewarded with a heroes' feast.

Divine Guardians

Sphinxes test the worth of those who seek the treasures of the gods, whether forgotten secrets or mighty spells, artifacts or magical gateways. Creatures that choose to face a sphinx’s test are bound to that test unto death, and only those worthy will survive it. The rest the sphinx destroys.
Some sphinxes are high priests of the gods that create them, but most are simply embodied spirits, brought into the mortal realm by devout prayer or direct intervention. A sphinx maintains its vigil tirelessly, not needing to sleep or eat. It rarely engages with others of its kind, knowing no other life except its sacred mission.

Magical Tests

The secrets and treasures a sphinx guards remain under divine protection, so that when a creature fails a sphinx’s test, the path to the object or knowledge it guards vanishes. Even if a sphinx is attacked and defeated, a quester will still fail to gain the secret it sought — and will make an enemy of the god that placed the sphinx as a guardian.
Benign deities sometimes grant a sphinx the power to remove supplicants that fail their tests, transporting them away and ensuring that they never encounter the sphinx again. However, those who fail a sphinx’s test typically meet a gruesome end beneath its claws.

Extraplanar Beings

Mortals that encounter sphinxes do so most often in ancient tombs and ruins, but some sphinxes can access extraplanar realms. A conversation with a sphinx that begins between tumbled stone walls might suddenly shift to an alien locale, such as a life-sized game board or a daunting cliff that must be climbed in a howling storm. Sometimes a sphinx must be summoned from such an extradimensional space, with supplicants calling it from its empty lair. Only those the sphinx deems worthy gain admittance to its realm.

Fallen Sphinxes

Whether through the weariness of the ages, regret at the slaughter of innocents, or dreams of worship by supplicants that attempt to bargain their way to knowledge, some sphinxes break free of their divine command. However, even if a sphinx’s alignment and loyalties drift in this way, it never leaves the place it guards or grants its secrets to any except creatures it deems worthy.

Androsphinx CR: 17 (18,000 xp)

Large monstrosity, lawful neutral

Armor Class: 17

Hit Points: 199 (19d10 + 95)

Speed: 40 ft , fly: 60 ft

STR

22 +6

DEX

10 +0

CON

20 +5

INT

16 +3

WIS

18 +4

CHA

23 +6

Saving Throws: Dex +6, Con +11, Int +9, Wis +10

Skills: Arcana +9, Perception +10, Religion +15

Damage Immunities: psychic; bludgeoning, piercing, and slashing from nonmagical attacks

Condition Immunities: charmed, frightened

Senses: truesight 120 ft., passive Perception 20

Languages: Common, Sphinx

Challenge Rating: 17 (18,000 xp)

The sphinx is a 12th-level spellcaster. Its spellcasting ability is Wisdom (spell save DC 18, +10 to hit with spell attacks). It requires no material components to cast its spells. The sphinx has the following cleric spells prepared:
Cantrips (at will): sacred flame, spare the dying, thaumaturgy
1st level (4 slots): command, detect evil and good, detect magic
2nd level (3 slots): lesser restoration, zone of truth
3rd level (3 slots): dispel magic, tongues
4th level (3 slots): banishment, freedom of movement
5th level (2 slots): flame strike, greater restoration
6th level (1 slot): heroes’ feast

Inscrutable. The sphinx is immune to any effect that would sense its emotions or read its thoughts, as well as any divination spell that it refuses. Wisdom (Insight) checks made to ascertain the sphinx’s intentions or sincerity have disadvantage.
Magic Weapons. The sphinx’s weapon attacks are magical.

Actions

Multiattack. The sphinx makes two claw attacks.
Claw. Melee Weapon Attack: +12 to hit, reach 5 ft., one target. Hit: 17 (2d10 + 6) slashing damage.
Roar (3/Day). The sphinx emits a magical roar. Each time it roars before finishing a long rest, the roar is louder and the effect is different, as detailed below. Each creature within 500 feet of the sphinx and able to hear the roar must make a saving throw.

• First Roar. Each creature that fails a DC 18 Wisdom saving throw is frightened for 1 minute. A frightened creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.
• Second Roar. Each creature that fails a DC 18 Wisdom saving throw is deafened and frightened for 1 minute. A frightened creature is paralyzed and can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.
• Third Roar. Each creature makes a DC 18 Constitution saving throw. On a failed save, a creature takes 44 (8d10) thunder damage and is knocked prone. On a successful save, the creature takes half as much damage and isn’t knocked prone.

Legendary Actions

The sphinx 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. The sphinx regains spent legendary actions at the start of its turn.
Claw Attack. The sphinx makes one claw attack.
Teleport (Costs 2 Actions). The sphinx magically teleports, along with any equipment it is wearing or carrying, up to 120 feet to an unoccupied space it can see.
Cast a Spell (Costs 3 Actions). The sphinx casts a spell from its list of prepared spells, using a spell slot as normal.

Lair Actions

On initiative count 20 (losing initiative ties), the sphinx can take a lair action to cause one of the following magical effects; the sphinx can’t use an effect again until it finishes a short or long rest:

• The flow of time is altered such that every creature in the lair must reroll initiative. The sphinx can choose not to reroll.
• The effects of time are altered such that every creature in the lair must succeed on a DC 15 Constitution saving throw or become 1d20 years older or younger (the sphinx’s choice), but never any younger than 1 year old. A greater restoration spell can restore a creature’s age to normal.
• The flow of time within the lair is altered such that everything within moves up to 10 years forward or backward (sphinx’s choice). Only the sphinx is immediately aware of the time change. A wish spell can return the caster and up to seven other creatures designated by the caster to their normal time.
• The sphinx shifts itself and up to seven other creatures it can see within in its lair to another plane of existence. Once outside its lair, the sphinx can’t use lair actions, but it can return to its lair as a bonus action on its turn, taking up to seven creatures with it.

A sphinx presides over an ancient temple, sepulcher, or vault, within which are hidden divine secrets and treasures beyond the reach of mortals.