Fable the lost chapters - burning swords

To do this trick you will need the multi-strike spell and at least two melee weapons (one of which must have at least two augmentation slots)

I can't explain what does this, however I believe you will need to select the weapon you want to "burn" and use the multi-strike spell, then switch to another weapon and back.

after this equip augmentations to the sword ( i don't know why this changes anything but it seems to) now go back to the game and see. There should be 2-3 times the amount of fire around your sword that was orginally there from the multi-strike spell, if not try teleporting to a different area as this also seems to do something.