|This spell hurls an exploding bolt of fire. This spell does not cost additional spell levels if the learner already knows Delayed Fireball.|
Fireball is a level 5 Conjurations/Fire Magic spell which launches an exploding gout of fire at the targeted tile, dealing unavoidable fire damage to everything caught in the ensuing 3×3 explosion. It is an excellent mid-game attack spell, allowing you to rapidly wipe out clusters of enemies.
Player-launched fireballs do
calc_dice(3, 10 + power / 2)
damage, which is less than Bolt of Fire but still respectable, and at a slightly lower MP cost.
Fireball is also unique in that learning it will consume zero spell slots if you already have Delayed Fireball memorized. This does not let you exceed the hard limit of 20 spells total.
If you learn the quirks of monster movement, you can potentially hit 8 monsters at a time with a single fireball. If your defenses are up to scratch, you may even want to take a hit or two to maximize your damage output, or to avoid running out of MP midfight.
Its unavoidable nature and burst radius and burst radius make it especially good for taking out annoying, hard-to-hit foes, such as bands of spriggans or opponents hiding in the back row. Firing it at melee range can be dangerous, however; unless you can aim at a tile behind the foe you're engaged with, you're likely to get caught in your own blast.