Here's what worked for me:
Code: Select all
[card]
name=Qasali Ambusher
abilities=reach
autohand=aslongas(forest,plains|myBattlefield) {0}:moveTo(myBattlefield) opponentblockersonly
text=If a creature is attacking you and you control a Forest and a Plains, you may cast Qasali Ambusher without paying its mana cost and as though it had flash.
mana={1}{G}{W}
type=Creature
subtype=Cat Warrior
power=2
toughness=3
[/card]