In its quieter moments, the cellblock is almost soothing. Its striking chequered floors, incongruous Escher-like architecture, and concrete walls adorned with chipped paintwork and bullet holes lend the space an unlikely degree of charm. Besides the light echo of peripheral footfall and HEV suit-charging it's eerily quiet. That is, until the Rebels step out against the Combine: barrel-chested, leather-skinned and bloodthirsty—an inevitable eruption of gunfire, pulse orbs and exploding frag grenades follows.

Since its arrival two weeks after Half-Life 2's mid-November 2004 launch, Lockdown has been one of Half-Life 2: Deathmatch's most popular 2v2 maps. Top players have came and went since, however TheRealQuAz and Maxtasy are long-serving veterans who've occupied its online multiplayer wargrounds since 2008.

Observing in god-like spectator mode, I look on in awe as these experts exchange blows with two lesser players; dancing around the map and executing fatal maneuvers with a level of precision that's owed to years of experience. Each dash, bunnyhop and meticulously-placed gravity gun-fired grenade is measured and is the result of refined strategy—it seems fitting the monochrome floor mirrors that of a chess board. Within mere minutes the commanding duo is fifteen points to the good.

"That was just a casual match," Quaz tells me afterwards. "The start was slow, but picked up toward the end when I got warmer."

Nowadays, casual matches are as good as it gets for HL2DM's most serious devotees. Of the 300 or so active daily players, around half are preoccupied with the game's Roleplay mode—a temperamental server which while hosting a huge map that lets players work, rent houses, commit crimes, and go to prison, isn't nearly as sophisticated—nor as fun—as it may sound.

"You have a bank account and earn money just for being on the server, and you can buy items with that money," explains Maxtasy. "A lot of people just stay idle on the server to farm cash. That's why these servers are usually at the top of the server browser and new players to the game usually join the most populated servers and get a weird first impression of the game, sadly."

Of the remaining 150 or so folk who tend towards the game's default modes, the chances of finding players fit to challenge the likes of Maxtasy and TheRealQuaz are few and far between. Of course this wasn't always the case.

In 2006, two years after the multiplayer's inception, HL2DM was a regular in Steam's top ten most played games, pulling in upwards of 20,000 players per day. For competitive players, Clans United was established as the game's central European community website and over a six year period hosted 1v1, 2v2 and 3v3 leagues which, at its peak, spanned five divisions with eight teams in each field. A hefty waiting list was perpetually on standby, whereby new teams would only replace outfits relegated from the lowest leagues.

The community always had some drama or scandal going on, whether it be cheating accusations, admin abuse or mismanagement.

At the same time, less significant forums such as HL2DM University were chartered, and a US ESL community ran a semi-successful 1v1 ladder. After players failed to shift Serino—no longer active but widely considered one of the best HL2DM players of all time—from the top spot after several months, though, the latter was eventually dissolved and absorbed by Clans United.

"Division one had some of the most skilled teams and players ever seen in the game," says Quaz. "It's strange to me that HL2DM was overlooked by the wider community considering the elite level of the top pros is so impressive to watch. But although host to some of the greatest matches ever played, the league and community always had some drama or scandal going on, whether it be cheating accusations, admin abuse or mismanagement."

In September 2010 Valve upgraded HL2DM to utilise the Orange Box version of the Source Engine—a move which disabled a well-used crouch bug that in turn vastly altered the game's bunny hop mechanic. For many players this meant relearning the game from scratch and compromised six years-worth of practice. As such, a number of teams withdrew from competitive play and by 2012 just two divisions remained.

It was then Quaz formed his first clan with two similarly prolific players of the time, Lancelot and Bangelo, who went on to win their debut season outright without dropping a single map. Normal procedure dictated that the top team would thereafter progress to the next league—in this case from division four into division three—however a coinciding league restructure levied by the game's admins saw the introduction of a new lower division, and thus saw Quaz and his team were forced to stay put. This didn't sit well with Bangelo and after several formal protests fell on deaf ears he quit the competitive scene entirely, causing Quaz and Lancelot to carry on in a separate 2v2 league.

In late 2012, Quaz gained admin rights to one of the remaining divisions, yet he himself was becoming increasingly disillusioned with the community due to several ongoing spats regarding team allegiance and admin disputes. Quaz describes the HL2DM scene as "stagnant" around this time and, having shared the gossip with Bangelo, passed over his admin details to allow his ex-teammate to browse the acrimony for himself.

"I gave the admin forum password to my teammate Bangelo with no malicious intent, just so he could have a chance to troll around on the private admin forums," Quaz explains. "Somehow he managed to delete the entire database of the site, much of which had not been backed up. Only an incomplete series of hall of fame pictures survived. This is pretty much how Clans United went down. I guess I owe it to the community to tell the whole story as they deserve to know and might not already."

From the outside looking in, it's difficult to view Bangelo's actions as anything but intentional. "To be honest, I don't remember all the details," Quaz adds. "I'm not sure exactly what happened internally but it had mixed reactions from the community—some people were obviously annoyed, including me, that much of the history of the game was lost. Others praised Bangelo for deleting Clans United as many players resented the management and felt its time had finally come. People just didn't care as much, despite Clans United being a cornerstone of Half-Life 2: Deathmatch for many great years, which is how it should be remembered."

In the wake of Clans United, the Old School Community was formed in 2013 which aimed to replicate and replace its predecessor. It's still live today however the same level of interest has never been achieved, and the OSC in its most modern guise instead caters for whichever 'top' players can be bothered stopping by. With other Valve franchises still hugely popular—not least Counter-Strike and Team Fortress 2—one might wonder why HL2DM has failed to garner the same long-term support.

Maxtasy describes his multiplayer of choice as "Valve's forgotten child", while Quaz points to the perceived steep learning curve of hitting top rank in HL2DM coupled with the advent of esports as possible reasons it got left behind—this and the fact Valve makes a killing from CS:GO's skin economy.

But I of course cross my fingers and hope for the best. My dream would really be a HL3DM game with huge support and a competitive aspect.

While both players have tried to invest time in the likes of Counter-Strike and TF2, unique weapons such as the Gravity Gun and how it's used in combat—"small nuances like lobbing frag grenades and catching them with the Gravity Gun can take years to master," says Maxtasy—combined with its skill-based movement and fast-action rounds have continually drawn them back to HL2DM.

So how does the HL2DM community move forward—can it? In light of Gabe Newell's Reddit Ask Me Anything last week, could the possibility of Half-Life 3 mark the return of Deathmatch? After all, the original Half-Life shipped with its own iteration of the Deathmatch multiplayer—perhaps a third series instalment of Gordon Freeman's otherworldly adventures is what this community needs to get it back on track.

"It looks to me that Valve is indeed working on a new game in the Half-Life or Portal franchise, but also I got the feeling their new game will be highly influenced by new technologies like Virtual Reality," says Maxtasy. "I fear the new game will be in VR, but I also doubt this will bring a new Deathmatch game. [Valve] already have their 'cash-cow multiplayer games' such as Dota 2 in the strategy genre, and CSGO in their FPS genre. But I of course cross my fingers and hope for the best. My dream would really be a HL3DM game with huge support and a competitive aspect."

Although slightly more confident, Quaz echoes a similar sentiment: "We will see it some day sooner or later I am sure, whether or not it will be called HL3DM is up in the air. However, I feel (and I hope I'm wrong) that it will be nothing like HL2DM. Considering the direction that FPS games in esports are going right now, it won't be anything like the classic arena shooter with skill-based movement. I hope I am very wrong and valve are saving HL3DM to be the revival of the arena shooter. But that may be wishful thinking from me."

In its current state, Quaz reckons the HL2DM community is done for. New players can never hope to reach high levels as there aren't enough top players to learn from. "The best thing in my view would be for Valve to create a brand new multiplayer FPS with a similar mechanic and aesthetic as HL2DM. Essentially a HL2DM reboot with a better competitive engine. I know that this would open up a world of unimagined possibilities. Whether they would be interested in that is anyone's guess. I would love to be involved if there ever was something of that sort."

Like the demise of any community, it's sad to see something once so active fade. But with Half-Life 2: Deathmatch it seems so many variables have worked against it for some time. It's trapped by the advent and ever-growing popularity of esports, and trapped by the Half-Life brand itself and the fact Half-Life 3 might never happen. It's almost ironic that HL2DM's most iconic map is set in a prison. Its most skilled players continue to battle on its dimly-lit concourse, every twitch trick-shot a callback to the game's energetic heday.