Some abilities and other effects refer to a hero or their targets being “on the ground.” Unless otherwise indicated, “ground” means any surface a creature could typically stand, sit, or lie upon, whether a castle’s stone floor, the dirt of a road, the deck of a ship, or a metal platform suspended high in the air.
Likewise, if an effect refers to a “ceiling,” that means any solid surface above a creature, whether a wooden tavern ceiling, the rocky roof of a cave, or an invisible wall of force.