Fiery Soul Trap is a weapon enchantment which, as the name suggests, adds both a Soul Trap and a Fire Damage effect.
It can be obtained by disenchanting the Steel Battleaxe of Fiery Souls found in Ironbind Barrow.
The fire damage of Fiery Soul Trap does not scale with Enchanting perks. However, Fiery Soul Trap does benefit from the Augmented Flames perk in the school of Destruction.
The Fire Damage effect of Fiery Soul Trap is enhanced by the Fire Damage base enchantment, making this a very effective combination for killing undead enemies, such as vampires.
The most notable trait is that Fiery Soul Trap allows for significantly more charges than the regular Soul Trap, making it the more viable choice.