Blacksmithing Primal Molten Warglaive Question

Finally got enough knowledge to craft my wife her warglaives for her DH. Now I’m looking at the crafting screen and trying to understand some stuff. Read a lot on WoWhead and IcyV but not completely sure I get it. I understand the secondary stat stuff as well as the embellishment, but what can I put in the optional reagent category/slot called “Infuse with Power”. I haven’t seen a list of items that go there (or I have and I don’t understand what I’m looking at). Thanks in advance.