Warpstone Flux Rating: ⭐️⭐️⭐️⭐️⭐️5/5 stars. I have a soft spot for the tortured World Eaters, but here in third edition, their rules work, and they are also nicely fluffy whilst giving attention to units who have really fell far to the Nails.
Background.
I feel sorry for the World Eaters. They were particularly doomed by the arrival of their flawed Primarch. Then, wanting to somehow become more like him, hammered the damned nails into their heads to heighten their rage. Their fall from grace could have been prevented at multiple turns, but most notably if the Emperor had actually helped Angron with his little slave rebellion. Who knows how things might have turned out differently (cf., Dornian Heresy). Later in the Horus Heresy, Angron ascended to daemonhood and became something else thanks to Khorne. Blood and skulls followed in the World Eaters path like never before.
Armoury.
Blades of the Fighting Pits. As per usual, you get to exchange chain swords for chain axes. This is good and comes recommended. It is also highly fluffy.
Caedere Weapons. Select from meteor hammers, excoriator chain axe, paired falax blades, and barb-hook lash. I remain a fan of the falax blades. Yet in all honestly in third edition all of them have potential. Even the barb-hook lash now gets not only a critical hit, but also a strength phage. On top of this [Legacies], your commanders, sergeants and so on can all take them as a replacement for a power weapon for a small points cost increase. This is to taste as the points cost does rise - sometimes too high, but it is fluffy.
Chain-Bonded. Select a Prime. Someone else in your army is his chain bonded brother who fought alongside him in the pits. Both get +1 to hit if in the same combat, so stick close together. This is super fluffy!
Tactica.
Violence Incarnate gives A+1 in combat in the turn you charged.
The Nails Bite is for the traitors. Fail a Ld test and you can become lost to the nails. This is good in some ways since you can get +1 to your set up moves, A+1, 10 on your advanced characteristics, but always have to make a charge move. You also get to remove all tactical conditions which is amazing.
Gambit.
Violent Overkill allows your additional wounds in combat to simply spill over outside of the combat. Beautiful!
Brutal Dismemberment gets you 2 additional combat resolution points if you remove your opponent, which is very nice for the show off wannabe champions of Khorne.
Additional Detachements.
Berserker Cadre adds 4 units but the 2 heavy assault ones must be rampagers. Useful.
For the traitors, Sons of Bodt gives you 2 supports that have to be apothecaries - or butcher surgeons as they should be called.
Advanced Reaction.
Brutal Tide is fluffy and appropriate and takes place when you are shot at. You get eternal warrior (1) which is nice and you must make a charge roll if you can which then results in you being locked in combat.
Furious Charge (they seem to have run out of original names at this point) is for the traitors and allows a unit to become lost to the nails after a volley step of a charge.
Overall, the rules for the World Eaters combine fluffiness and effectiveness. They're really good!