Thousands are playing Valve's unrevealed shooter Deadlock, a blend of Team Fortress 2 and Dota with Bioshocky skyrails

rockpapershotgun.com:

Valve's third-person hero shooter Deadlock hasn't been officially revealed yet, but thousands of you unscrupulous devils have been playing it thanks to stolen development builds. Speculation abounds that these "leaks", coupled with Valve's obstinate silence about it, are a calculated publisher psi-op. Are they deliberately letting people play the game early so as to temper the marketing rollout in some way? Perhaps handle any early player criticism under cover of non-announcement? It seems unlikely, but as other writers have pointed out, this is Valve, unaccountable elder god of PC gaming. I guess we should be thankful it isn't another Half-Life tease.

The scale of the leaks means we have a pretty solid idea how Deadlock players. In particular, the Verge's Sean Hollister has wangled his way into playing a few rounds of the leaked build, publishing some thoughts and thereby attracting the wrath of Valve's orbital banhammer.

The short version is that this is sort of Overwatch and Team Fortress 2 with more of a MOBA-style, lanes-and-creeps component, and a steampunk setting that reminds me of Dishonored's Dunwall (also, a microtransaction store, but you were expecting that). It's a 6v6 affair, and each team gets a retinue of NPC Troopers who spawn continually at your base and attempt to conquer a series of enemy positions. Smash through every opposing fortification, and you'll reach their base and fight their Patron - a huge, flying orb with arms. The game's heroes (there are 20 in the leaked development build) get light and heavy attacks plus a parry.

You can also trade resources from slain enemies for special abilities as the match goes on - for example: lifesteal, energy barriers, some kind of electro-grapple - but you can only do so back at base. Which is where the game's skyrails come in: these Bioshock Infinitesimal fixtures allow for rapid travel up and down each map lane. According to Hollister, the skyrails are laid out away from the map's major firing lines,