This question concerns the Lady Mikage fusion. I pulled Locwain before I accumulated all of the rares below him. Can I just take Locwain to 5/50 or do I also have to take all of the lower rares to 4/40?
You can just use Locwain. Be aware, though, that once the fusion is complete, you can't do it again - so, if you want to keep a copy of Locwain for whatever reason, you'll want to fuse the rares before finishing the fusion.