Rain of Fire

Base Spell Description
Instantly deal (combinded active towers' damage) x3 to all enemies.

Requirements
 is available for purchase right off the bat with no wave requirement. You can purchase the base level of  for 5. Each level upgrade up until Level 10 will increase the cost by 2x. From levels 11 to 15 (once you have the appropriate Tournament upgrade) the spell cost increases by 3x.