Hey fam -
The endlessly helpful, profoundly informative taxonomy of unlockable challengers located here attests that Lukien, that grey, runic dude, presents himself as a BC opponent if you visit his store front for "several consecutive days." He hates customers? I dunno.
I have been window shopping with no bites for 4+ days; does one have to buy a potion on each visit, or do the hula for him?
I.e. if any of you masters of battle have insight into getting this guy, I would be deeply grateful.
We had a problem with unlocking Lukien actually being broken at first, as long as you are consecutively visiting him each day (and I'd assume around the same time) you should have unlocked him, so you may need to file a ticket if he still hasn't showed up after one week.