Originally posted by Hoakin Blackforge:

Just how does the weapon infusion works? Only for centesian weapons?

Place any Unique-quality weapon (the ones with the golden border) in the left slot, and any other weapon in the right slot. The only catch here is that the right-slot weapon has to be a higher level than the left-slot item.

You can see the level of the weapons in each slot displayed next to the slot. Make sure that the number on the right is higher than the number on the left, and you're good to go.

Thanks! Time to farm bones and kill everything on sight!