User blog comment:ClariS/Why Xerath's Passive is Bad/@comment-66.177.229.41-20130319221803

"Also, his passive doesn't even make sense with his lore, or theme."

Not true. I think the concept here is that the more AP he has (keeping in mind that he is basically made out of energy, albeit the chunks of floating matter that he consists of) the more armor he will procure, reciprocating from the fact that the arcane energy sort of works as a magnet to strengthen the bond and perhaps aquire more fragments of the runic skeleton he embodies.