All creatures 'flying high' suffer D6 S6 hits, and are forced down to earth, re-entering the table on their own side's table edge in their following turn.
One use only. Skaven wizards only.
Note that in this case flyers are merely forced down to the ground, they are not 'driven off" in the manner of flyers defeated in hand-to-hand fighting. Consequently, the flyers are not obliged to miss an entire turn off the table, as are flyers which have been driven off from combat.