Introduced in the Burning Crusade expansion pack, the Gronn are monstrous, Cyclopean creatures that reside in Outland, immortal demigods of the Ogre race. Some say the Gronn gave rise to the lesser Ogres, yet if so, they show little inclination toward liking them, given that they are tyrannical rulers. According to canon, there is rumoured to only be seven Gronn in existence, and they are not famed for their intelligence.

Gronn resemble massive Ogres, hulking and tremendously muscular, with bony, rocky, blood-red bodies covered with hard lumps and spikes. They are also covered with painted runes and symbols. They have only one eye, and are likely inspired by the Cyclops. They always carry huge clubs, truncheons, or rocks for hurling at foes.

These Ogre demigods were first mentioned in the Burning Crusade trailer at BlizzCon. Their image was also shown, but not identified until the release of the bestiary, several months later.

Two of the known Gronn are in Nagrand. The other—nicknamed The Hungerer—is an extremely potent foe.

Farther north, in the Blade’s Edge Mountains, more Gronn have been seen. Canon legends tell of a lair (the Gruul’s Lair instance) in that area where the greatest of these Gronn (Gruul [see below]) may be located.

Known Gronn:

Gruul the Dragonkiller, the raid boss in Gruul’s Lair is supposedly the father of the Gronn, and the most famous of the Gronn themselves. The greatest of the Gronn mentioned above is Gruul.
The 5 known sons of Gruul: Goc, Gorgrom the Dragon-Eater, Grulloc, Maggoc in the Blade’s Edge Mountains and Durn the Hungerer in Nagrand.
Given that it is said there are only 7 Gronn known to exist, two remain after Gruul’s sons; Nath is speculated to be the final Gronn.
There are a few elite monsters in Nagrand, called Mountain Gronns, that are walking around near Warmaul Hill and will fight with Ogres. These are probably lesser Gronns, or a step between Ogre Lords and Gronn.
At The Circle of Blood in Blade’s Edge Mountains there is a NPC, Baron Sablemane that has this to say: “My loathing of interruptions is overshadowed only by my hatred of Gruul the Dragonkiller and his seven sons!” So we can safely assume that Gruul doesn’t count amongst the 7.
Speculation: Given that both Durn and Maggoc are described as Gruul’s sons, Gruul may be the first Gronn, or else the being who created them (if this is the case, then Gruul might not count towards the total of seven). Given the use of the term “demigod,” it’s logical to assume that Gronn are comparable in power to the Azerothian variety, such as Malorne, Cenarius, or Aviana.

But, among the demigods of Azeroth, there are huge differences in power. There are the mightiest demigods, such as Malorne, Cenarius, Aviana, Agamaggan, Ursol and Ursoc, but then there are the lesser ones, such as the little guy with the sickle, the six-legged wolverine, the tiny fox among others.

It is most probably so, that the seven Gronn are demigods, but that there are differences in power amongst them, just as with their Azerothian counterparts. Gruul the dragonkiller is the mightiest one; as mighty as Cenarius, Malorne or Aviana, albeit in a different way, while the other Gronn, Durn, Maggoc, Nath, and the patrolling ones are lesser demigods, akin to the lesser Azerothian demigods. It has however been noticed at blizzcon about gronnkings wich are probably the step over gronnlord, they were probably destroyed when ner’zhul tore the planet apart.