Carnifex
A Carnifex is a monstrous Tyranid creature from the Warhammer 40,000 game. Carnifexes are hulking beasts that are often used quite literally as battering rams, barging through enemy lines and tossing tanks around like toys. However, the Carnifex is among the most customizable of Tyranid units, allowing for many different varieties to fulfill different roles on the battlefield. They range from the above mentioned battering ram, to a weapons platform for anti-horde duties. 'Fexes are notoriously resilient, and can even be upgraded with regeneration - a mutation previously unique to a Carnifex special character known as Old One Eye, but later introduced to the standard Tyranid army list - making them extremely difficult to kill; It's pretty much a diet Robo-Terrasque. 40k players commonly name specific variations of Carnifex by taking another word that represents the concept and appending "-fex" to the end. For example, the Dakkafex is a shooty Carnifex based on the Ork term "dakka".
Note: In Latin, "Carnifex" literally means "butcher," but is also used for an "executioner," a "tallow-renderer," or, more figuratively, a "murderer" or "villain."
Carnifexes in 5th Edition
In the 5th edition, the Carnifex lost a total of eighteen biomorphs and weapon options, having been replaced by more stringent mandatory loadouts. The Carnifex has also faced a doubling in base point cost with rather paltry statistical increases - putting it arguably somewhere between 20-30 points too expensive for the overpowering majority of competitive army lists, and 10 or so points above the cost-effectiveness ratio provided by variant 'Fexes (such as DISTRACTION CARNIFEX).
How profoundly infuriating this is for Tyranid players writ-large cannot be denied, and is notable for being one of the first times that players openly called foul on Games Workshop. Beyond any doubt, the Carnifex was the mainstay big fucking unit of Tyranid players and was the one unit that literally every Tyranid player had in their army list. It was the epitome of ubiquitous; you could mount lots of options on it, and all of them, to some degree or another, were viable - until this edition hit. This is most Likely because Games Workshop wants more money and by making the Fex suck you have to buy, from Games Workshop, the Trygon to stand a chance.
Some of the new biomorph weapons and options were nice, and there was options added to make some of the 'Nid swarm a little less vulnerable to being dramatically outgunned, and considerably improved Tyranid psyker units (its command units especially), but in the process, the Carnifex - the one fucking model every 'Nid player and their grandmother had at least one of - got toned down dramatically and is now rather inefficient - as well as much more vulnerable to being taken down quickly by certain units with reasonably-effective armor-penetrating weapons (of particular note: Guardsmen with Missile Launchers, Hunter-Killer Missiles, Rubric Marines, Necrons, and Stormtroopers, since the fucking thing can't take Extended Carapace anymore.
It enraged players even more that this edition's weapon changes functionally forced people to buy all-new Carnifexes since the old ones they fielded, such as Sniperfexes (which were armed with Venom Cannons and Barbed Stranglers, to give the Tyranids much-needed fire support and allow them to stun enemy vehicles into submission) were no longer valid, whilst several of the new bioweapons, whilst not bad (people like that the Venom Cannons can score penetrating hits now) are specifically designed to take bites out of the Carnifex's originally-legendary punch (since the gun now replaces 2 hands). Functionally, the Carnifex is now half as good at ranged support as it was before with only token upgrades in return and the loss of about 33% of the Carnifex's durability, since it can no longer shrug off a lot of weapons it used to. The new rules for blast weapons (of which the Heavy Venom Cannon is one) doesn't exactly help the Carnifex's average accuracy, either, which renders its tankbusting potential rather lacking on top of all this.
Extensive debate on /tg/ has been had since the update, arguing whether the new Carnifex is a direct result of corporate evils or the result of gross incompetence or prejudice on the part of Robin Cruddace, the 5th edition codex writer. As of currently, smart money is on the former; it's widely known that GW is bleeding money due to its fuck-ups, which indicates that this may have something to do with it, especially since Robin Cruddace isn't exactly the biggest fan of Tyranids. Which sort of makes him a reverse Matt Ward.
Again, there are a few bright spots. 3rd edition's Old One Eye is back, even if he does now cost more than a Landraider and is barely better than a standard Carnifex with no weapons courtesy of Old One Eye's close-combat only biomorph loadout (his primary advantage is that he recovers wounds of fives or mores instead of just sixes, which isn't worth it at all.) The new Hive Guard is a great unit for fucking with Communist Dipshits that like to use the old Fish of Fury tactic. Wider support for variant weapons, previously from Chapter approved, are also a plus. It's a shame that the good stuff gets out-fucked by the bad.
Carnifexes in 6th Edition
In 6th the Carnifex saw a buff with a nice price drop from 160 to 120 points bare. However some of the weapons they can use have seen a nerf, notably Scything Talons and Crushing Claws (Although their point cost also decreased). The Carnifex gets it's biggest bonuses riding the monstrous creature buffs that came around in 6th, such as the ease of cover save availability and the sweet hammer of wrath attack you can make when you charge into battle and swing with D3 S9 I10 attacks to sucker punch some unlucky guy. Fear is generally useless and should not be relied upon to make much of a difference, however if it does take effect the Carnifex gains a big in combat boost vs. its natural prey.
The Carnifex has gotten better with its tank crushing power, now that they have Armourbane and no longer strike at I1. Walkers like the Dreadnaught and Soul Grinder still strikes before the Carnifex (so equip electroshock grubs and entice them to charge), but they can now deal with Power Fists without suffering a blow from them. Otherwise the carnifex still takes apart vehicles with record efficiency most of the time. Also people field a few less anti-tank weapons in favor of more anti-infantry power due to 6ed move away from mech warfare, not huge but it helps a bit to have one less railgun rammed down your fex's throat. Oh, and if your Carnifex falls out of synapse range, it haves a 50% chance of eating itself if theres more than one in a Brood! Even by themselves they can't get shit done because they aren't allowed to shoot, run, or even assault unless it can charge the closest enemy unit (Even a squad of TH/SS Terminators). It no longer gets Rage unless you roll a 6, even then it still follows the 5th edition Rage, so keep them in Synapse range!
All in all the Carnifex is now a viable choice to field and is now more versitile with the choice to go either Two Twin-linked Brainleech Devourers, a Cannon of your choice with Crushing Claws, or even just stock equipment with Regeneration to act as an escort for a Tyranid Prime. Old One Eye is still a meh choice, slightly better, but lacks the buff other HQ can give to your army while not being a solid enough HQ to contribute its own to the battle in any real way.
(With 6th second force org chart at +2000 point games, you can field a total of 18 fexes, that's about 72 T6 wounds and up to as many as 126 S9 attacks on the charge (If raging, but that heavily relies on luck) and could go up as high as 180 attacks with crushing claws on Vehicles(very unlikely, but hella scary to think about)!
Carnifexes in 8th edition
So far so good, it seems. They've seen a MASSIVE reduction in price, going from 125 points in 6th/7th, to a mere 67 points base, though, you need to pay at least 20 extra to actually field one. They've been moved to the elites slots like the 4e fexes of old, and you call still squadron them without any limitations on points like the old 4e fexen. Though it seems they aren't getting armored shell back, they are receiving a pretty substantial buff in a couple of ways. First and foremost, they're the rough Dreadnought Equivilant of the Tyranid army, with T7, 8W, 3+ save, S6 (With a weapon option that brings them to S12 AP -3, with 3 damage per hit that goes through. (Not really reccomended due to -1 to hit, however, unless your tagging along with OOE), and being a monster/vehicle that doesn't degrade. Though, bringing it down somewhat from its potential are two factors: One, unless Old One Eye is tagging along with them, their weapon skill is a mediocre 4+, basically 5+ if using crushing claws. Not terrible when you have 6 attacks on the charge, unless you have crushing claws in which case its even worse, but not ideal. The other being is when they are taken either shooty or vanilla, their S6 isn't particularly threatening compared to your other options for dedicated melee in this edition like the Swarmlord, the aforementioned OOE, Trygons, Haruspexen, etc. Overall, an extremely solid unit with a bargain price. Getting roughly the equivilant of a Space Marine dreadnought. Good all-rounder unit, from the sounds of things, especially with the option to make squads of them. We'll have to wait and see how it turns out, but it seems the days of Fexen mediocrity are over.
Old One Eye
Old One Eye is the only unique Carnifex in the entire Tyranid Codex, along with being one of the few unique characters in said codex. He's known for being ultimately fluffy but not the slightest bit crunchy. He has nothing to back his fluff up.
Old One Eye is a Carnifex that was present when Hive-fleet Behemoth came to fuck the Ultramarines' world of Calth. Now, like most Carnifex, his armor was nigh impenetrable. Reaching around the problem, a soldier ignored his armor by aiming a plasma bolt at his head, searing right through his eye and into his skull. The beast was declared dead. He was quickly forgotten, his corpse freezing up during the winter and left behind after his Hive-fleet was obliterated.
Some time later, some scavengers found the ice block and thawed it out, hoping to get some cash. (Yes, they decided to follow the plot of Jason X, I would say more like the movie the Thing.) However, like a defeated hero who has to do a sequel, he quickly regenerated his wounds, save for his original plasma scorched eye. He fucked their shit up, ravaging Calth along with the Tyranid remnants from the original invasions. Rumors were spread of a terrible, single eyed beast hunting the terrified population, earning the creature the title of "Old One Eye." You see, despite being cut off from the Hive Mind, skull fucked by a plasma bolt, and frozen, he was still alive. His long stay on an Ultramarines world had earned him a skill that none could counter: Plot armour, rivaling that of the Ultramarines.
The Ultramarines, unable to stop him with regular means, sent in Scout Sergeant Telion, the greatest scout sergeant/sniper in the Imperium. Telion hunted OOE down, cornered him near a cliff, and managed to disable him by shooting his ruined eye socket, causing OOE to stumble into a large ravine die yet again. However, since he was plated with the same plot armor of the Ultramarines, he survived and traveled around Calth, ravaging more and more Imperial cities. Now, this wasn't OOE's only plot armored moment. OOE has been hit on numerous occasions that would outright killed a regular Carnifex. Rumors abound that the creature was killed dozens of times, only to get back up again like some Necron player who owns cheating amounts of good luck with his Reanimation Protocol rolls.
Nowadays, its frozen body has become a bit of an attraction for a local Genestealer Cult, who worship its corpse alongside their Patriarch.
Table-top wise, OOE was first introduced in the 3rd edition as one of the two only Special Characters for the Tyranids, who otherwise had no individuals among them. Back then his cost was relatively low (slightly higher than a decent kitted out fex) and came with his unique Crusher Claws. Regeneration was also unique to him, allowing him to AUTOMATICALLY regenerate one wound per turn as well as get back up from being dead on a roll of a 4+ (there was no limit to the number of times he could do this). He was also unique in that he was the only special character that could be taken in an army less than a certain points value (all other characters had a minimum points value to field them. OOE had a Maximum Point value). Needless to say, this was when he reigned supreme since you had something that cost around the price of a dreadnought that can dish out an upwards of 8 attacks on the charge AND ignore wounds. He was removed in 4th edition because it was felt that Tyranids should not have characters within them, as they are a faceless swarm, so OOE's abilities were given to normal carnifexes. This end up kicking the bucket in 5th edition, where he returned but with a boost to his overall point cost while not regaining his borderline-OP regenerative abilities (He still had the claws tho). In 6th edition OOE is a unique HQ choice who's more expensive than a regular Carnifex (30pts less than a Land Raider), while not being able to significantly outperform one. In the retarded 5th Edition that is when the Tyranid army went to the shitters, much like the 5th edition space zombies (Check your 6th edition, Necron are now at the top of the heap). So yeah, he's going about, being one of several, excellent avatars of what is wrong with 5th Edition (Cptn. 6th edition here with your morning news, Old one eye; still bad, but a little better get him into close combat and he'll SMASH SOME HEADS).
In 8E, it seems OOE is turning out a bit better. He's more durable then the average fex, and gives them a bonus to their Weapon Skill when he's near them. Not much else is known about him yet besides the fact that he finally costs less then a land raider.
Stone Crusher Carnifex
Even nastier and more 'battering ramming' Carnifexes, used as living siege engines. They have a bevvy of special rules making it even easier for them to knock down buildings (never a big problem for 'fexes, but a job's a job), and reduce incoming fire strength. They aren't bad melee 'fexes even if your opponent has no buildings, though, and are reliable enough investments to a stompy 'nid list.