It was trademarked by Riot a year ago. Screens were shared showing a log-in screen and card templates. Merrill regained control and confirmed Supremacy was a prototype.
The operative word being 'was'. Reportedly the hacker said more would be revealed about the abandoned title until Marc Merrill emailed him saying not to.
"This is the real Marc," tweeted the Riot president. "Account's back in my hands ...."
"Yup, someone got onto my Twitter account. Yup, someone shared some old screens from one of the many prototypes we've experimented with," he explained. "We're always working on a variety of new ideas for League & beyond. Lots of experimentation that may never see the light of day :)."
League of Legends: Supremacy seemed to be an awful lot like Blizzard's Hearthstone. The hacker claimed to have the "server and client source" for the prototype, adding it was "fully completed" but held back from release. They posted images of the deck templates via an imgur gallery. A public service announcement or just plain criminal?