User blog comment:FairyRaven/Fairy Tail Chapter 427: Pitched Underground Battle, Review and Commentary/@comment-24277053-20150406142622/@comment-7418318-20150406143129

I wouldn't jump to conclusions just because of this chapter. Abel just said that he has the doll from Kain, but what do we really know?

It might have been stolen, might have been a gift. For all we know Kain turned from active Dark Mage to Dark Mage teacher/curse-doll maker and Abel was one of his students.