User blog comment:ND999/Lore Hypothesis, Mt. Targon, Guardian Sea and Shadow Isles/@comment-6582248-20141116014213/@comment-11556861-20141116103926

Hm, but now - look at BoTRK active - steals % of targets maximum health and ms. Mordekaiser ult - steals % of targets maximum health and after the target dies he gains stats (AP and AD)

I agree on Morde posibly being Ruined King, but now I also have diffrent theory that I came up with just today (and as such it is not so great yet)

What if Mordekaiser isn't Ruined King himself, but rather his brother? We now know, from Kalista quotes, that Ruined king ordered the ritual because of grief, probably after losing someone close to him - at first I assumed that it may have been his wife or someone like this, but what if it was his brother, who lost his life in battle? Ruined king ordered the ritual to revive him, and the ritual succeded, creating the first undead Mordekaiser, but the ritual also unleashed power none could expect and destroyed whole isles.

If Mordekaiser and ruined king were brothers it would be only natural they could have similar abilities - Mordekaiser ulti and BoTRK active.

Also, if he was brother of the King, he surely would be having high rank in shadow isles. So Altars calling him Lord and his old lore that stated he was one, make sense.

Next, if Mordekaiser was a warrior (Battle-mage?) Who died in battle, he probably would be buried in his armor, maybe when they revived him, they accidentaly also sealed him into his armor, prisoning him, and his powers inside it? That is possible!

If that is the case, Mordekaiser now would seek for something that could free him out of it. So... Where could he find such knowledge? He probably would start searching in old magic tomes. And one magnificent chamber filled with magic books was in noxus. And when he was looking for anything that could let him do that, a mage, the owner of library, lured by noises, came to the chamber and found Mordekaiser... and the rest of that story is known.