Zelos, Irelias brother is no longer mentioned after he leaves to get help from demacia. So what ever happens to Zelos?

Died I assume

Iirc, he left Ionia to get help from Demacia right before Noxus invaded, and he never returned. People speculate he'll return as a champion some day

I consider everything pre-death of the JoJ non-canon anymore

look at rivens lore then look up journals of justice issue 10 mind = blown

Kraken ate his ship on the trip over.

@Melancholy Exile and Cerubois:
I think Xaki is referring to the Warrick article. The one where he is captured and tortured by someone (Warrick assumes it was a guy because of his voice) wearing a Zaunite bio-hazard suit. This guy taunts Warrick about all of the children Warrick killed in Ionia. Then he removes his mask and reveals he has a half melted face.

Ultimately you get the idea that this was an Ionian, male, that survived an attack from one of Zaun's Melter squads. If it was Zelos it would explain his disappearance for a while; he would have been recovering from his wounds then going rogue (I assume that last part). It is all conjecture, but it seems plausible to me.

Zelos would have had to go rogue before disappearing, in that case. :P

He was on a mission to Demacia to request help. Would he abandon that quest and go fight Melter squads (and their creators) instead? Seems rather illogical, given his status and devotion to Ionia.

It kinda has nothing to do with Riven's lore either way... That barrage was carried out by Singed. >.>