Yes, TYRANNIES is a Scrabble word!

Letter values in Scrabble US: T 1, Y 4, R 1, A 1, N 1, N 1, I 1, E 1, S 1.

Is it a valid word?

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

a form of government in which the ruler is an absolute dictator (not restricted by a constitution or laws or opposition etc.)
dominance through threat of punishment and violence

Also: authoritarianism, one-man rule.

Not playable in Scrabble US: STALINISM.