User blog comment:Xilinoc/Ch. 632 - friend 2/@comment-24531362-20150625111720/@comment-1338810-20150626041805

Wasn't Yhwach's whole thing that his easiest prey were people who were missing something internally? And they would seek out his power which would make them complete while basically selling their souls to Yhwach after they died. I figure that's why Yhwach latched onto Haschwalth - he could tell Haschwalth's powerlessness would make him more likely to accept Yhwach's essentially Faustian deal.