I understand that the reference to the ruler of the Shadow Isles said by the Altars on TT but who is the Ruined King?
Karthus would would the most sense first but he's a mage which doesn't make sense regarding the item and he isn't really a king, he just likes death (what a fucked up guy)
So what are your theory's Who is the Ruined King of the Shadow Isles?
I recon the Ruined King is a man who was tempted by Mordekaiser down the path he chose. Due to grief over something; likely the death of a lover or family member, Morde offered him the chance to bring them back, leading to the Shadow Isles.
I'm also of the opinion he's a different person to everyone else that we've seen come from the Shadow Isles.
Yep, totally 
Isn't the Ruined King thought to be Hecarim? 
The Left Altar does say "Remember who you once were Hecarim" And there are a bunch of Reddit posts about it.
Karthus is not from the Shadow Isles, he just grew to have a fascination with it and death.
As for the other candidates, I believe Hecarim was his body guard, many people think it was Mordekaiser, with others thinking Mordekaiser was the usurper who took advantage of the ruined king. I think those are the only Shadow Isle related characters that are actually relevant.
From my remembrance Hecarim and Morde were generals of the Shadow Isles or something among those lines, not the actual king.
Some people argue the blade actually has nothing to do with the Shadow isles and is actually a reference to Tryndamere, although its a good theory, it doesn't really fit since Trynd has no relations with the blade in-game while shadow isle champions like Kal seem to know about the history.
Kalista knows of the ruined king, however has no relation with morde or Hecarim, which gives me further reason to believe it isn't them.
In short, I don't think we are given a name yet.
It is most likely riot just fucking with us :(
I wonder What he's doing now as an undead king. I wonder what kind of Activity goes on in the Shadow Isles currently.
He sure has left you all RUINED HA HAHAH
I think im a go back and fix that
