EDIT: Dark Star Varus was just revealed on Riot's Instagram.
Out of nowhere, Riot dropped a major teaser on us. On the League of Legends Facebook page, a short video titled “Dark Star Thresh” shows what might just be the next Legendary skin. You see a Thresh hook shoot through a dark hole and people standing around in the Void, League ’s dark abyss. You can hear the chain warden say: “Can you feel it? Your future... torn away. There is no escape. Only oblivion."
You can even see Thresh’s head in the last few seconds. It looks like a cross between Kindred, Aurelion Sol and the Yu-Gi-Oh! card Stardust Dragon . Putting all the pieces together, you can even figure out what this new skin will feature. The chain shooting out of the black hole comes out in a bright light, I expect Thresh’s chain to shoot out like a star and his lantern to be a tiny dark void hole. I’m guessing that Dark Star Thresh will be covered in a cloak of the night sky, with a brand new voiceover and will cost 1820 RP.
Moobeat, the warden over at Surrender@20, thinks that it’s not an Ultimate skin over a Legendary:
Expect Dark Star Thresh to appear on the PBE pretty soon.