Homebrew Sphinx Species Details

Guardians of secrets and treasures of the gods.
Age: Sphinxes are immortal beings, having been watching over the world since they were first summoned during the First Age. While immortal, a Sphinx may choose to end their life when they feel they have grown bored of it. Most sphinx tend to live for thousands of years, however. Sphinx age and mature at about the rate of humans, reaching maturity around 16 years of age. Though they cannot die of old age or illness a sphinx can still die of injury
Alignment: Sphinxes are strictly lawful creatures. They have a tendency to ere on the side of neutral, however, as they have few issues committing acts some would see as evil as long as it aligns with their own code of law.
Size: Sphinxes can be very large beings, but the average sphinx adventurer tends to be in their younger years. Because of this, they have not reached their full size, which takes hundreds of years to do so. The average sphinx adventurer is about 7 feet from foot to head and weighs 400-600 pounds. Their size is Medium.
Inscrutable: They are immune to effects that would sense their emotions or read their thoughts, as well as any divination spell that you refuse. Wisdom (Insight) checks made to ascertain your intentions or sincerity have disadvantage.

Sphinx Traits

Ability Score Increase. Your Intelligence and Wisdom scores increase by 2.

Never Unarmed 

You are never unarmed. Your claws are weapons with which you have proficiency. If you hit with your claws, the target takes slashing damage equal to 1d6 + your Strength modifier. At 5th level you use a d10 and your claws are now considered magical.

A Truly Magical Creature

You have resistance to psychic damage and cannot be magically charmed or frightened. You are also resistant to bludgeoning, piercing, and slashing damage from nonmagical weapons. 

Sphinx Truesight

 At level 5, when you are within 60 feet of a visual illusion, you automatically detect its true nature and succeed on saving throws against it. At level 10, when you are within 60 feet of a shapechanger or a creature transformed by magic, you can determine the true form of the creature. At level 15, when you are within 60 feet of an invisible creature or a magically hidden door or object, you can see it. At level 20, the range of all of your Sphinx Truesight abilities doubles.