Yes, INCASES is a Scrabble word!

Letter values in Scrabble US: I 1, N 1, C 3, A 1, S 1, E 1, S 1.

Is it a valid word?

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

a ruler of the Incas (or a member of his family)
a member of the Quechuan people living in the Cuzco valley in Peru
the small group of Quechua living in the Cuzco Valley in Peru who established hegemony over their neighbors in order to create an empire that lasted from about 1100 until the Spanish conquest in the early 1530s

Not playable in Scrabble US: INCA, INKA, INCAN.