Yes, LABYRINTHS is a Scrabble word!

Letter values in Scrabble US: L 1, A 1, B 3, Y 4, R 1, I 1, N 1, T 1, H 4, S 1.

Is it a valid word?

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

complex system of paths or tunnels in which it is easy to get lost
a complex system of interconnecting cavities; concerned with hearing and equilibrium

Also: inner ear, internal ear.