Curse of Flesh

The Curse of Flesh is a curse suffered by many titanic creations, notably the dwarves. The curse changed the structure and appearance of these races from their original stony/metallic forms into the fleshy forms we know of today.

The Curse of Flesh is revealed to have been created by the Old Gods early in Azeroth's history to "facilitate assimilation". The titans attempted to remove the curse (and the Old Gods), but found that the Old God infestation had grown too severe to remove without completely destroying Azeroth. Instead they bound the Old Gods within Azeroth.

Brann Bronzebeard
A dialogue triggered by Brann Bronzebeard in Ulduar and Halls of Stone gives most of the details of the curse and the connection to the Old Gods.

Fizzcrank Fullthrottle
In the quest, a dialogue with Fizzcrank Fullthrottle details the removal of the curse from several gnomes by Gearmaster Mechazod which transformed the gnomes into "mechanical beings". The dialogue mentions that all creations of the titans eventually fell victim to it.

Sjonnir the Ironshaper
Sjonnir The Ironshaper mentions the curse when engaged.

Therazane
Therazane mentions the curse during her gossip text for the quest Quest:At the Stonemother's Call, while pointing that those afflicted with it killed her daughter, Theradras.

Siamat
In the quest Traitors!, Siamat transforms three Tol'vir into Onyx, saying "Your makers failed you... your race succumbed to the curse of flesh! Lord Deathwing's gift makes you perfect again!"

Discs of Norgannon
While the Lorekeeper's Knowledge in Uldaman doesn't mention the Curse of Flesh by name, it clearly refers to the same events that are later described by the Tribunal of Ages. Interestingly, this dialogue was written during the original World of Warcraft, indicating that either this plotline has been planned for many years or has been built out of existing lore.

Jotun
Jotun's title suggests that he is cursed, or bears a curse to others (which could be believed to be the Curse of Flesh).

Archavon
In Archavon's Log (before Patch 3.3.0), for the Day 1051213, Archavon wrote "Archavon wake up, notice face feel soft. Not important. Go back to sleep." This could hint that he was, more or less, affected by the Curse of Flesh.

General Bjarngrim
While General Bjarngrim in the Halls of Lightning does not directly utter the name of the curse, he does refer to it during the fight. His quotes imply that he compares himself with the player. Apparently, he also considers killing lifeforms affected by the curse to be the the solution of removing it.

Lady Deathwhisper
In Icecrown Citadel, some of her dialogue states that the Curse of Flesh is a joke played by the Creators on their own creations. She also states that the sooner the cultists come to terms with the 'fact' that the Curse is a defect, the sooner they will come into a position to transcend it.

Earthen/Dwarves
The Tribunal of Ages dialogue reveals that it was the curse that caused the transformation from stony earthen to fleshy dwarves while they were asleep in Uldaman.

Stone troggs/Troggs
The troggs too, were initially stone creatures. Like the Earthen, some were affected by the curse, turning them into fleshy troggs.

Mechagnomes/Gnomes
If Gearmaster Mechazod is to be believed, prior to the curse, gnomes appeared as mechagnomes. Unaffected mechagnomes have been found in the Storm Peaks, maintaining the mechanical systems of the Titans.

Tol'vir
The tol'vir of Uldum are a race of stone cat-centaur introduced in Cataclysm. The curse of flesh causes them to turn into the fleshy, wingless version of themselves. The process can be reverted by powerful beings such as Siamat, and is a some kind of a 'reward' for swearing allegiance to Deathwing.

Earth elementals
The curse of flesh can effect the various earth elemental types within Deepholm. This causes them to turn into creatures akin to fungal giants. However, it may be that earth elementals view biological matter itself as a curse, independent of the Curse of Flesh.

Vrykul/Humans
Sjonnir the Ironshaper appears as a vrykul with metallic skin. As such, it was thought possible by some players that the vrykul also had an original, more stony, appearance and also suffered from the curse. However, the 'iron' races were constructed by Loken, after and separately from all other titan creations. Instead, based on the quests and, it is thought that the birthing of humans may have been originally a severe side-effect of the curse on the vrykul.

Aesir, the storm giants
The storm giants of Northrend may be aesir who have succumbed to the curse. Aesir is the titan word meaning "storm giant".

Earth elementals
Pygmies and Ettins might have formerly been some type of earth elementals, too.