The fireball tag is a copyright tag, obviously intended for posts that deal with the Disney/Toei series starring drossel_von_flugel. Not so obvious is what to tag images that depict balls of fire. There are a few such posts under fireball, a few more can be found under fire_ball, fireball_(fire) and fireballs. None of these tags have a wiki page.
(I have a ghostly half-memory of this issue being discussed at an earlier time, but the forum search gives no results.)
Updated by jxh2154