Baelfire (BAYL-fire)

A decidedly demonic power, Baelfire is half literal fire and half metaphysical force. It can set things physically ablaze, but it can also consume their essence - not so much reducing them to ash and smoke via combustion, but rather reducing them to nonexistence via compelled entropy.
Things consumed by Baelfire are irrevocably gone from the universe; wounds inflicted by it are wickedly painful, often crippling, tortuously slow to heal and quick to leave horrifying scars. A mortal killed by it is destroyed utterly: the fire is fed by their very soul, and once the soul is consumed it is burnt from existence entirely, never returning to the Cycle or to whatever paradise its gods might once have offered it.
However, while Baelfire is technically capable of consuming a soul and reducing it to nothingness, it takes a great deal of effort to do so, along with either a prolonged duration or a truly massive firestorm. Though Baelfire lingers longer than completely mundane fire, it is difficult to sustain such a flame in the absence of direct concentration on it, and so generally it will burn itself out long before it annihilates an entire soul.
In essence, it's not the sort of thing that can be done casually or by accident: one would need to be specifically trying.
Only a select few servants of the Dark God are allowed to possess the ability to produce and manipulate Baelfire: the Torturers of the Demon Realm, for one, use it to punish evil souls, fueling the hellish machines, contraptions, and magical goings-on both within the Dark God's domain and without. Powerful Warlocks and Blackguards can also be granted such a boon, as well as an Avatar of the Dark God.