Or just have him tap into his innate demonic heritage. He is, after all, a demon. He just fights for the Machina. I'm sure he could create his own blade or plant creature that he can siphon blood from like a sap, use that to control Victoire's flowers, and get into a power struggle with her and her kind. 

And then he can create another plant that's a sniper who shoots Victoire while she's fighting Bonesword for control.