Skrix, Startled Stalwart

Skrix, Startled Stalwart enters the battlefield tapped and doesn't untap during your untap step.
Whenever another creature enters the battlefield, untap Skrix, Startled Stalwart
and it fights that creature.
———{line}{line}{line}{line}{line}{line}{line}{line}{line}{line}{line}{line}{line}{line}
"What was that?! Who's there?!"