Yes, SPHINXES is a Scrabble word!

Letter values in Scrabble US: S 1, P 3, H 4, I 1, N 1, X 8, E 1, S 1.

Is it a valid word?

SPHINXES is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

an inscrutable person who keeps his thoughts and intentions secret
(Greek mythology) a riddling winged monster with a woman's head and breast on a lion's body; daughter of Typhon
one of a number of large stone statues with the body of a lion and the head of a man that were built by the ancient Egyptians