"I popped his eyes and drank the goo"
(Skylord Vitali on the Skylord Unknown's death)
'Theory' It could be assumed that Skylord Unknown is Skylord Valetius. This could be said by how when Skylord Valetius appeared in the Yogscast Tekkit series (Duncan's Laboratory) it was two years after Skylord Vitali's rampage on the Skylords (after people's debates on Skylord Unknown). So it could be assumed that Skylord Valetius was featured in Tekkit for us to speculate whether Skylord Valetius is/was Skylord Unknown. And as Tekkit is on a totally different server to the Shadow Of Israphel server it doesn't mess with the storyline at all. Reasons that this could be plausible; Skylord Valetius wear's purple googles over his eyes that could give the impressions that they could be purple from blood mixing with black, and so his eyes could have been gouged out. And he was seen after fans realisation on a missing identity of a Skylord.
Also another theory that could have an even bigger explanation for why Skylord Valetius could be Skylord Unknown and why he appears in Tekkit could be that he is going make a appearance in the Shadow Of Israphel series.
Skylord Unknown could possibly not be dead, my points for this are; his part of Vitali's poem is the only part that could be thought possible to survive, "I popped his eyes out and drank the goo." Nothing really suggests he's dead, as having no eyes is not really a big deal in the series, as shown by Angus Eyeless. But the chest with the remains in. That chest may possibly not be the remains of Skylord Unknown, as the chest did not have a sign with his name on it above it, the chest wasn't that close to his part of the poem, and it could be thought that the remains in the chest were actually Skylord Baako's... This could be said by how no one cleaned up the mess of the exploded Skylord, like Lewis/Xephos quoted "Well that room over there is full of, like... Blood and exploded Skylord remains." Leaving the blood thirsty vampire (Skylord Vitali) to cease his remains for his own hunger, and putting savoury bits in the chest for later.
In a poll that was held from January to February 2013 on this wiki with all Season 3 characters to choose from, the Skylord Unknown was placed equal 26th overall with 5 votes out of 4412 votes.