Pg.15 original rules: What a creature can do on their turn.
• Do Nothing
Sometimes, your creature will have nothing useful to do. Or, it may be affected by a spell or condition that prevents it from taking any actions (like Stun). In this case, you can choose to “do nothing” for its Action Phase. Even if your creature does nothing, you must still flip its action marker to the inactive side.
I know the question has been answered. And I would never try steal Skytails thunder. But I thought I would show you the exact ruling.