I recently found a unique item, which had an affix which is also a gem affix. Like all gem affixes, there is a mana cost and a level requirement listed for the gem type.
Does the item then have an inherent mana cost due to the affix?
What equivalent gem level does the affix attach to the item (i.e. lvl 1 or item base level?)
Does the affix level up like a gem?
I gave it to a party member so I cannot test it.
In this instance: Culling Strike