Yes, HADES is a Scrabble word!

Letter values in Scrabble US: H 4, A 1, D 2, E 1, S 1.

Is it a valid word?

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

(Greek mythology) the god of the underworld in ancient mythology; brother of Zeus and husband of Persephone
(religion) the world of the dead

Also: infernal region.

Not playable in Scrabble US: PLUTO, AIDONEUS, SCHEOL.