Hellgate: London debuted in 2007 with an interesting setup that was brought low by half-baked execution. It went under a couple of years later, came back as a free-to-play MMO that didn't really go anywhere, took a run at Steam Greenlight in 2014, and I'm not really sure what happened after that, to be honest. It's been quite a ride. And it's not over yet, because HanbitSoft, which acquired the rights to the game a decade ago and redeveloped it as Hellgate London: Resurrection in South Korea, is bringing it back to Steam in November.
The description on the Steam page is a little mangled, but the new-old game will apparently be singleplayer (the original was also designed primarily for solo play), and will include the Hellgate: Tokyo content that was planned for Hellgate Global, which ultimately never saw the light of day. Again, it's all kind of confusing.
As for the game itself, Hellgate: London is a near-future action-RPG set in a world that's been invaded by demons. Think Diablo (and in fact, original developer Flagship Studios was built around a core of Diablo veterans), except the whole planet is Tristram (opens in new tab). It's got six character classes, each with unique skills, abilities, and customization options, and features randomized dungeons, quests, and items. Hopefully the campaign from the initial release is back too, but the Steam page makes no specific reference to that so we'll have to wait and see.
I can't help but admire the determination to find an audience for Hellgate: London, and I kind of understand it, too. To me, it's always seemed like a game that, with a little more polish and a good break or two, could be a properly successful series. I'm not alone in thinking so: In our "Reinstall" from several years ago we said it "missed some opportunities" but was nonetheless "an engaging experience and a bold attempt to bridge the gulf between genres."
The "re-release" trailer above is the one you'll see on Steam, but I really prefer the old one from way back when.