Welcome to Deathgate, home of the Doom Burger, can I take your order?
This is an artifact fortress. All craftdwarfship is of the maddest quality. It is adorned with rings of text. It menaces with spikes of animals. It is decorated with adamantine awesome. On the fortress is an image of Overseers in demon blood. The Overseers are cackling insanely. On the Fortress is an image of animals and CPU. The animals are milling about. The CPU is in the fetal position. On the fortress is an image of the BATTERY and physics. The Battery is producing power from nothing. The physics is weeping. On the Fortress is an image of dwarves and demons. The dwarves are striking menacing poses. The demons are decomposing. On the fortress is an image of dead cats in cat bone. The cats are self-referential.
—Blade Master Model 42
Deathgate the Doom-Fortress is yet another Dwarf Fortress succession game hosted on Bay12 Forums and launched by AnimaRytak in May of 2011. Compared to other succession forts, it lacked some of the insanity and massive bloodshed that made Boatmurdered and Syrupleaf epic. It made up for this by being for being the first succession game to successfully invade hell.
In universe, the story is as follows...
The year was 751, during the Age of Fairy Tales, the dwarven kingdom of The Basement of Murder sent forth the group known as the Death-Hammers of Wrath to found an outpost in The Windy Plane. Seven dwarves set out from the mountainhome, Fistmachines, with their heads held high and their beards soaked with booze. A year after Deathgate's founding, the first overseer goes completely insane after learning the Death-Hammer's true goal to invade and conquer hell.
And thus begins a tale of horrible things. Half a dozen overseers are driven mad, hundreds of dwarven lives are lost, thousands of goblins slain, and several demi-gods rise and fall. Hell is invaded, conquered, and a fortress known as the Hellbunker is established. In Deathgate, dwarves are born, they are raised, and they die. Even after the rest of the dwarven kingdom has crumbled, Deathgate remains defiant.
The fortress finally met its end on December 13th, 2012. 
The sequel, Murdermachines, is now underway. 
Unrelated to The Death Gate Cycle.
Both Fortresses Provides Examples Of:
Anyone Can Die: Par the course for this series. Even incredibly badass dwarves are mortal.
Badass: Now both forts have had many notable Badasses, the most spectacular of which are listed in each.
Doomy Dooms of Doom: The first fort's full name is Deathgate the Doom-Fortress. The sequel is Murdermachines the Blood-Citadel
Eldritch Abomination: Terry, the anthropomorphic avatar of Deathgate's save-game corruption, became this in-universe. In the sequel, every named dwarf has become one of these. AnimaRytak takes the cake as it's implied he merges with Terry during the first death of the fortress.
Made of Iron: Paindeer. It's your average deer, which somehow survived not one but two hits from a siege ballista and which wandered around for a while with vital organs hanging out of its body.
In Murdermachines, the Voidspawn are this. They can endure enormous amounts of physical punishment thanks to insane immunities.
Mundane Utility: Both fortresses now have their own version of the BATTERY and both are practically not used at all.
At least not yet, MurderMachines is still going on and there is a massive unfinished project that might actually use the full capacity of the BATTERY... or not.
Deathgate Provides Examples Of:
After the End: Dwarven civilization has collapsed; the dwarfs of Deathgate may be the last members of their race.
Karakzon was, until his death from a broken spine, a very effective combatant. His Blood Knight tendencies led to him biting a Forgotten Beast. His protege, Tryrar, was similarly badass.
Germayne, the leader of the marksdwarf squad, had over twenty-six kills to his name.
Logem Bomrekikal, Ultimate Fucking Badass, an untrained, one-handed woodcutter who managed to slay four goblins in mere seconds before being struck down by a hammer blow to the face.
Badass Army: Deathgate's current army is becoming this, after NCommander decided that it would be a good idea to drown the military in the trade depot. This caused their strength stat to shoot through the roof to nearly double that of normal dwarfs.
In addition, Deathgate now has elites in its military as of 777.
Bizarrchitecture: The fortress is known for being extremely hard to navigate thanks to a maze of twisting passages, abandoned storerooms, and flooded throne rooms. It's just not a decent turn if the player in question doesn't come onto the forum halfway through asking "what in the hells was THIS room meant for?"
This got to a point where to get anything done(and stop dwarves from dying of thirst)they had to seal entire sections of the fort.
Bunny-Ears Lawyer: The Mad Fool in-universe. He's not a very good doctor, however he's the only one Deathgate has.
The Mad Fool: Progress! The subject survived the procedure, or at least he was still alive when he stopped screaming. He's dead now, of course, but that's hardly relevant.
Butt Monkey: One dwarf, nicknamed Kelsa, somehow lost both legs and and arm in an unknown incident.
Two early militia dwarves were each missing an arm. This was not grounds for a dismissal.
Murderedmachines has had a dwarf push a minecart despite having no legs. How? Using his arms and teeth is the current theory...
Crapsack World: By the time Deathgate opens, the elves are extinct, most of the dwarven fortress have fallen, and the humans worship Llama Demons.
Crazy Awesome: noodle0117's battle of hell became this. Using a series of homemade traps, two well-timed cave-ins, live goblin drops and an obsidianizer, he took out the entity of the clown rush with only a single fatality
noodle0117: Deathgate has never seen a finer day.
Death Course: The bridge leading to Deathgate's main entrance was lined with many deadly weapon traps. Said bridge was responsible for the death of many trolls.
The courtyard leading into the Hellbunker was supposed to be packed with adamantine spikes, but something went wrong and they never entered operation, thus resulting in the deaths of many dwarves.
Dissonant Serenity: Derm, one of the previous mayors, was creepily calm with the amount of death and murder going on in his fort.
Do Not Go Gentle: Overlaps with Last Stand. During the final battle between the elves and the humans, the humans brought a force of over 500 strong. Only 23 elves and four grizzly bears were left. The end result?
Noloc Istro, "The Battles of Burning"
A: 525, mostly humans, 215 losses
D: 23 elves, 4 grizzly bears, 23 losses
Attacker was victorious.
Do It Yourself Plumbing Project: Deathgate has had several of these. All three aqueducts running into the lower fort have either sprung leaks, threatened to flood the fort, or have spontaneous had trees grow to block the outlet.
Dug Too Deep: Invoked. Not only did the inhabitants of Deathgate dig into hell, they invaded and conquered it.
Evil Weapon: The Red Monster Sword, a sword made completely of !!Fire!! To date, it has never been used in combat as anyone who attempts to wield it is horribly burnt, and a fair number of dwarves died simply trying to carry it to the shrine built for it.
Fun with Acronyms: Big Acceleration Transforming Transistor Extracting Raw Energy Yield
Crazy Awesome Recon Patrol
Ghost Town: Vast sections of Upper Deathgate are practically abandoned due to the majority of the population relocating to Lower Deathgate. Many of the bedrooms and workshops have not seen use in several years, and at this point the surviving dwarves wouldn't really make a dent in the facilities anyway.
Giving the Sword to a Noob: Untrained recruits are often given adamantine equipment, despite barely understanding how to use any of it.
Haunted Castle: One goblin adventurer was choked to death by the ghost of a woodcutter.
Heel-Face Turn: After getting killed by the dwarves, the soul of one of the demons took a year as an Overseer and spent the year watching the dwarves and trying to goad them into doing selfdestructive things. The result was one of the bloodiest years in a while, but when he was done, Lashidang gave up in disgust at how little the rampant horrors and rapidly-spreading demon sickness bothered the dwarves, and decided to reincarnate as one on the grounds that they were worse than the demons.
Here There Were Dragons: Happened during worldgen; the dwarfs had managed killed off the last two megabeasts, but by time they succeeded so few people were left that the world passed into the Twilight Age. Hundreds years later, it became the Age of Fairy Tales; this only happens when pretty much every fantastic race and megabeast are dead.
kefkakrazy: By the way, the final confrontation with the surviving Fire Bros took place in the Hellbunker's booze stockpile, so the responding dwarves had to deal with haunt of fire blasts in addition to the occasional shower of boiling booze. I suspect that flaming wine was the cause of Super-Cat's death.
Kick the Dog: One sadistic overseer dumped hundreds of live animals down a deep pit just for the fun of it. (It was also to boost lagging framerates, but mostly for fun.)
Kill 'em All: One overseer's solution to the pet population.
Lava Pit: Used to execute several dozen goblin and troll captives.
Lethal Joke Character: During a number of demonic outbreaks, some random bystanders somehow survived significantly longer than the others around them. A dwarven child lasted longer than several adults against several fire demons, and so did a cat. The king of these, though, is the legendary Darkwing the Netherfowl, a duck so amazing that he singlewingedly made ducks a primary Deathgate mascot; Darkwing accounted for two demon deaths.
Mad Doctor: The Mad Fool exemplifies this trope. In-universe, he is an insane doctor who more often than not kills his "patients".
AnimaRytak: The upper system was never really complete and because of the deaths it was causing, it was shut down.
Dariush: You aren't true dorfs!
AnimaRytak: Noodle died three times on it!
Man Bites Man: A fortress champion, Karakzon, used his teeth against a Forgotten Beast.
Mundane Utility: noodle0117's BATTEREY stands out. It was built as a super-powerful dwarven water reactor, able massive amounts of power to operate any number of Pointless Doomsday Devices. Instead, for almost the entirety of its life, it was used operate a single millstone.
Paint the Town Red: The primary bridge leading into Deathgate was, for a time, painted almost entirely blue due to the large amount of trolls that had been massacred in their attempt to breach the fortress.
In addition,the floors of both the Hellbunker and hell itself are coated in demon and dwarf blood.
noodle0117: I might need a bit more time getting the update up, since my computer literally crashed from the sheer amounts of gore, death, and dwarven engineering awesome.
Syndromes carried by that blood have infected the vast majority of the fort population, leading them to all have painful blisters of their feet from touching it.
Ragnarok-Proofing: Averted with the BATTEREY. After it was shutdown, numerous large mushroom trees began to grow inside the water channels, eventually this blocked the water flow, and rendering the device inoperable. Parts of it were eventually savaged to form part of the BATTERY.
When wlerin needed to regain to Upper Deathgate, he punched a hole into the BATTEREY's inner workings. The main path runs along abandoned and broken axles, and many missing floor tiles before leading up a ramp to a long disused door that leads into the BATTEREY hall.
Real Life Writes the Plot: The save file became so badly corrupted that it was no longer possible to run the game for more than a few seconds. It was declared in-story that Terry had trapped the surviving dwarves in a time loop to savor their suffering.
Redshirt Army: The high fatality rate among the military has turned them into this. The loss of many of the better military dwarfs has left Deathgate woefully under defended, and unable to replace those losses in a timely matter. See We Have Reserves below.
Virtually every new overseer begins their turn with something like "This place makes no sense at all". Also see Bizarrchitecture.
People requesting their dwarf's status while stating how likely it is to have died.
Every time the foundation is laid for a functional military, the next overseer typically finds a way to kill, maim, or skewer half the recruits before the first seasons end.
Typically, most named 'dorfs' suffer short lives after being named. Noodle stands out as a particular case, suffering numerous deaths in during [AnimaRytak's] third turn. Baelor "The Bastard" II had his second dorf selected, named, and killed in the span of about an ingame month... and the death took place within sight of the ghost of Baelor I.
Due to unknown errors in the save game, certain graphical glitches are common. The community blames this on Terry, the anthropomorphized madness of Deathgate (the same one that drives overseers insane in-universe).
Temple of Doom: The Temple of Armok was this. Complete with a sacrificial altar. That never really worked right.
Total Party Kill: "I had an update ready, but I wound up... well, I accidentally our entire military."
Training from Hell: CARP training involves this. The military was locked in the trade depot while water from the aquifer was pumped in.
Volcano Lair: A slightly less malevolent version. Emphasis on slightly, with the occasional exception of demons coming shooting out of the volcano.
We Have Reserves: Subverted later in the fortress's life. Migrant waves, the main source of replacements for the military, ended when the dwarven civilization crumbled. It is possible that the citizens of Deathgate are the last remaining dwarves in the world. Which (as of NCommander's turn) stands at 56. When Deathgate dies, the dwarves likely die with it.
You No Take Candle: During their various descents into madness, several of the fortress overseers begin to speak like this.
Murdermachines Provides Examples Of:
Badass: Like its predecesor, Murdermachines is home to many, but of most recent note is the Recruit Mafol◊. As a recruit with no military training whatsoever, he killed three Forgotten Beasts!
Stunned players had this to say:
"What the f***. Is some random undorfed recruit now our new Darkwing? Hell, even Darkwing just managed to kill two clowns before he went down. It's beyond me that a frigging recruit in the Official Voidspawn Feeding Detachment managed a triple kill on Forgotten Armokhumping Beasts." -Kefkakrazy
Barred from the Afterlife: All the dwarves of Deathgate were barred from entering the Golden Halls of the Stonemaker. Instead they spend an eternity in limbo before invading another world.
Beware the Quiet Ones: During the First Fall of Murdermachines, the fortress population was so low and so crippled that the only dwarf left even reasonably healthy was the one-legged fortress doctor. Unfortunately, the fortress doctor was The Mad Fool, terrifying mad scientist, and he ran around beating a number of the invaders to death with his crutch before finally getting himself wounded. The kobold who finally crippled him? Before he passed out, Mad Fool ate his kidney. While it was still inside him.
Body Surf: The in-universe explanation for the succession of dwarves with the same nickname.
Curb-Stomp Battle: Anything that The Void God participates in pretty much counts; he butchers armies without a scratch. The slaying of AMBASSADOR, the Forgotten Beast that effectively caused the First Fall of Murdermachines, also counts; after the fortress was reclaimed, all the hostiles on the map relocated to the surface, where AMBASSADOR was decapitated by a goblin lasher shortly after the reclaim began.
Deadly Training Room: Pretty much self-explanatory. It's the reason that the Void-wraiths are able to liquify most foes without casualty. It isn't particularly plot important and isn't often mentioned, except in passing.
Did We Just Have Tea with Cthulhu?: CaptainMcClellan before he even began playing his turn befriended Terry, who had gained enough power and sentience to take up a presence on the forum. This resulted in his immediate promotion to Overseer, along with Terry's promise that he wouldn't tamper with his reign. Also, to a lesser extent, lolfail's Pokebattles with Terry.
God in Dwarven Form: AnimaRytak, the Void God. Watching him fight is less akin to battle than it is to an episode of Will it Blend.
Good Bad Bugs: This IS Dwarf Fortress, but most amusingly with the voidspawn. They were intended to be able to convert enemies into voidspawn Thralls with a poison attack, but a bug with the way this works causes the newly-born Thrall to continue to be hostile to its "parent" if it survives melee combat with the Voidspawn for long enough for the poison to work.
He Who Fights Monsters: Played with. While the original dwarves of Deathgate have become worse than the demons they once fought, it was not fighting them that made the dwarves into monsters. It was getting rejected from the afterlife.
Hopeless War: The state of Murdermachines following the First Fall. Reclaim parties were not pleased to find that they spawned onto the map in the middle of a four-way war between the Forgotten Beast AMBASSADOR, a voidspawn war party, an army of previously-captured goblins who had escaped their cages, and the kobold raiding group that originally caused the First Fall. It took the emergence of The Void God to recolonize the fort, and the surface is still more or less a deathtrap.
Mauve Shirt: See Badass above for Mafol. Before this event he had zero kills, no player name, and noone knew who he was. Afterwards, well, he made the tropes page. Need I say more?
Moral Event Horizon: In the backstory, the dwarves of Murdermachines crossed it before the fortress even began. At this point, the fortress is so wired with half-finished deathtraps, barely-contained super beasts, and automated childcare/torture chambers, that it's barely possible to get a plate of plump helmet biscuits without committing a crime against nature.
Mordor: The area around Murdermachines doesn't resemble the scorched hellhole of many other famous Fortresses, but what it lacks in flaming death it makes up for in sheer nastiness. Huge mounds of treasure, weapons, armor, and furniture are piled around the fortress... along with the bodies of anyone who ever tried to claim any of it, because the sheer amount of hostile traffic the fortress exterior gets is astonishing.
Real Life Writes the Plot : The reason why after ChaosMaker's successful in-universe coup, he handed over the fort over to Peregarrett was real life obligations on his part leading to him being unable to take the fort on his turn. This was quickly lampshaded by saying that ChaosMaker had "more important things to do" and handed over official power to what was basically to be a "puppet Overseer".
Rule of Cool: The rule of cool is taken for granted with Dwarf Fortress, but especially at MurderMachines where it seems to have taken on force of law and is used in decision making both in-universe and by the writers. Terry and perhaps also ChaosMaker seem to base all of their decisions of the level of amusement they will get out of it.
The Coup: The in-universe explanation as to why ChaosMaker took over the fort when CaptainMcClellan was going to retain the throne. There were also implications that Terry's protection had run out. Or even that Terry himself wanted McClellan gone because the fort was too orderly.