Purgatory Dragon Slayer Magic

Purgatory Dragon Slayer Magic (煉獄の滅竜魔法 Rengoku no Metsuryū Mahō) is a form of Caster-Type Lost Magic and Dragon Slayer Magic that revolves around the user of fire

Description
This form of Dragon Slayer Magic, like all others, probably grants the user the characteristics of a Purgatory Dragon and revolves around the use of the element fire. However, not much is known about it. The differences between this and Fire Dragon Slayer Magic were not explained and it's only use was to cast a gigant fireball