Roughly the end of the Second Era so well before any Elder Scrolls game we've played so far. The Dark Elves see Morag Bal's influence in Cyrodil as something that should not be happening ever and so decide to fight... and take the throne while they're at it. They respect the Nords and the two groups had an alliance to deal with the Akavirii that invaded shortly before. The Argonians didn't have anyone else they could ask really seeing as Cyrodil is the problem... Though the "free all [Argonian] slaves" clause the managed to get was a definite plus. The Noridic king is nominally in charge though in truth the ruling body is a tribunal made of one representative of each race.
Basically ESO is where Merunes Dagon got the idea for the Oblivion Crisis. We all know how THAT turned out.
On to the actual art, who found whom first and which one, the Argonian or the Nord decided that three nigh immortal and ridiculously powerful beings being drunk in the same room was a good idea? I might have entertained the idea that the Elf brought it up, but I don't think I see any influence of Shogath on him... could be wrong.<br / />