Prepared Battleground

This spell gains Flash and costs {1} less to cast
if an opponent attacked you with 3 or more
creatures this turn.
Attach Prepared Battleground to target tapped
land you control when it enters the battlefield.
Sacrifice fortified land: Roll a dice. Destroy all
attacking creatures with even converted mana
costs if the number is even. Do the same for
odd numbers if an odd number was rolled.
Fortify {2}