Devil's Third is a gem that's never really going to be capable of being experienced again just because so much of it was tied to being experienced as an online game. The single player and score attack is decent, especially if you know enemy weaknesses (notably the black armored soldiers, which are usually considered to be damage sponges, die in two melee shots if I recall correctly), but the multiplayer really was where you could tell Valhalla Games wanted you to have all kinds of fun with.
In the online mode, you could go it alone as a mercenary, or after ranking up a little bit, you could join a clan. I personally joined a clan after lone wolfing it for a while and getting recognized in online matches by the clan leaders of the two top clans. They liked me so much that they ended up sending me invites to join their clans with the in-game customized "clan propaganda".
Upon joining a clan, you became a part of a constant struggle for territory between clans. Each map represented a portion of territory in the United States and you could see which clans had control of each territory by looking at the multiplayer menu. You'd be assigned a place to build your base after joining a clan and be tasked with fortifying it with defenses and placing buildings and traps to make it hard to attack should a siege occur. This all played into the Siege mode where one clan would attack another in hopes of destroying their customized base and gaining territory.
This stuff was wild and really innovative. If the game was bigger this kind of clan conflict would have been even more impressive as I'm pretty sure diplomacy and chat communication was a big thing for clan leaders. Clan leaders had their own private chat for discussing clan matters if I recall. If the game was more popular you'd probably have people that were dedicated mercenaries too that joined either side for siege battles and weren't a part of the greater clan struggles (we had a couple players like this who left clans to become mercenaries over clan drama, was neat). I think because the game was so small, clan leaders ended up setting up times for sieges to occur so as to prevent going in and destroying a base when no one on the other side was around to stop it (I think this stuff ended up happening regardless though as clans grew more competitive some became more slimy lol). There was a whole rather light economy thing going on with making more money to build fortifications and chatting with other members of your clan for fun and sometimes talking strategy for siege battles. And if you really weren't into the base building stuff, other clan members could do that in your stead I believe.
And that's just the clan stuff, the more traditional quick get-in-get-out modes like battle royal and team deathmatch were all awesome. Probably the only shooter where I actually love all the modes and it's a bummer that some of them weren't always very active. Having a clan helped organize when you could play those modes. All the weird and unique modes were so much fun, Chickens: where you tried to maintain the largest trail of chickens, Ignition: Bringing a bomb to an enemy bombsite to detonate it, Carnival: throwing fruit into a giant blender that would rise and sink into the ground at different spots in the map, Close Quarters: Melee Weapons only (not the best of modes because the melee was so limited but the lethality of that mode was palpable), Gladiator: everyone starts with no weapons, just their fists, and random weapons will spawn on the map leaving everyone trying to run to points of interest to get weaponry, and etc. etc.
The modes were really great. The maps were too. The whole switching between first person shooting and third person melee action seems like it doesn't really work or that it works with caveats if you only play the single player. However, in multiplayer, the blend worked perfectly. Killing two players with a shotgun in the middle of a melee skirmish, slashing a guy in half with a katana while they're sniping with their back to you, and one hit killing people in a small building by throwing a literal sledge hammer right in their face. It all worked really well with the map design and both options felt suitable to use for a variety of situations. The weapon variety was great with everything from flamethrowers and axes to rocket launchers and tomahawks. Albeit this stuff wasn't as balanced as it could have been, one of the bigger tragedies with this game is that it never received balance updates and a select few players would abuse exploits with rocket launchers that were straight up incapable of being countered due to how easy it was to be staggered by explosives.
But yeah, really great game. Probably one of the best experiences I've had with an online game and it's probably the sole reason I'm really open to playing them nowadays. It had great mechanics, charm, and character customization. I know some people ragged on the multiplayer for having some microtransaction elements, but they really were so minor at the time. They gave you so much of the in-game currency dedicated to the that microtransaction stuff for ranking up and you got a ton of it for getting all the collectibles in the single player. I got pretty much everything I wanted without having to drop a cent nor feeling pressured to. I remember being being confused when some reviewers brought it up as it was extremely tame in comparison to bigger budget games. It's still not great to have mind you, as their is some good gear with some stat bonuses that you inevitably won't be able to get without putting in some serious time ranking up or ponying up some cash. But if you had specific stuff in mind that you wanted, you definitely could get that specific stuff with just the currency they give you.
But yeah, I'm done rambling I think. I really wish the team was able to give it another shot because it really is something special, but I doubt it. Interestingly enough they released Devil's Third Online for PC in the west under the name of RockShot as free-to-play title on Steam but it got shut down after a mere three months. I remember trying it for a bit, but my PC couldn't run it very well at the time and I'm pretty sure a ton of maps and weapons were missing along with the microtransaction element being considerably worse (renting weapons for usage if I recall correctly lol).