The highlight of PAX Prime this year was, as it often is, seeing what independent developers have been up to since PAX East. We loved Tharsis, Brigador, and interesting projects like YIIK, but our favorite game of PAX was quietly nestled into the Alienware booth: a playable build of Warhammer: End Times - Vermintide, the four-player cooperative melee game set in the fiction of Warhammer fantasy.

Swedish developer Fatshark opened it up for us after the show floor closed, letting us jump around in levels that weren’t accessible to the public. What’s surprising about Vermintide, and absolutely central to its appeal, is how fresh it feels despite its deep similarities to Left 4 Dead. You wade through swarms of Skaven, Warhammer’s ratling bad guys, as you move from the beginning of a map to the end, struggling along the way to survive ambushes from Elite Skaven that toss poison grenades, shoot you with miniguns, or pin you to the ground until an ally saves you. At the end of a level, I lugged explosive barrels from one point to another as more and more Skaven spilled into the level, killing four or five of them at a time with wide-arcing swings from my actual warhammer to keep my AI and human teammates safe.

It’s an indisputably familiar formula for any Left 4 Dead player, but that familiarity only added to my comfort level with the combat and controls, and the Skaven themselves have much more personality than the mumbling zombies of L4D. The Skaven will chirp at you. They’ll turn tail and flee in the event that you outnumber them. And most significantly, they’re proper melee fighters. The lowest-level slave rats are simple to dispatch with a single, hard swing from an enchanted flame sword or a shot from your crossbow, but handling the armored Stormvermin soldiers, for example, takes careful blocking, distance, and timing—all of which are tough to manage when a swarm of a dozen-plus Skaven are encircling your team. Depending on what type of melee weapon you have, you’ll have to apply a heavy attack (activated by holding down Mouse 1) to even injure them.

Nuances like that make you realize how barebones Left 4 Dead 2’s melee combat was. And in combination with Vermintide’s loot and inventory systems, it seems like there’ll be a greater incentive to grind levels at higher difficulties. Finishing a map on a harder setting will result in more loot dice, which could produce rarer gear for one of Vermintide’s five heroes, but there’s even a twist on Left 4 Dead’s “Gnome Run” that connects with the loot system. Fatshark showed me a well-hidden nook of an early level, a cellar obscured by shrubs that held a Grimoire, a scary-looking book with moving eyes embedded in the cover. Equipping it reduced the health of the whole team by a chunk, but if we made it to the end of the level with this handicap we would’ve been rewarded with the possibility of more loot. Multiple Grimoires can be used in a single level, too, to up the ante even further.

The melee system is the star, and Vermintide’s iteration on the core, sound ideas of Left 4 Dead made it the best thing we saw at PAX Prime this year. In budget, scale, and personnel, this is Fatshark’s biggest project ever, and from what I’ve played they’re managing gracefully.