PowerOff
Turns off the specified/assumed/elicited player.
Invocation options (choose based on grammar-fit):
Alexa, [ open / start / launch ] MediaServer
Alexa, [ ask / tell ] MediaServer [ to / for ] …
power down
turn off {Player}
power off {Player}
turn off my player
power down {Player}
power off my player
turn off the {Player}
power off the {Player}
power down the {Player}
turn off {Player} player
power off {Player} player
power down {Player} player
turn off the {Player} player
power off the {Player} player
power down the {Player} player