Traag were huge extra-planar black panther creatures in the I.C.E. Age history, with horns protruding from their heads, ever dripping poisonous claws and double rows of venomous teeth. They were predatory loners who preferred darkness and residing in subterranean chambers. While they were not demonic themselves, demons and traag would never harm each other. Traag had the innate ability to summon demons at will, and would let powerful ones ride them. It was rumored there were "traag lords" on some unknown plane of existence who knew all of the spells for summoning the demonic.
Uthex Kathiasas implied he had traag originally in the Dark Grotto, which by implication of the word was artificially formed by the magru, except that the magru apparently ate them all in their need for flesh. His name for the magru was "lug'shuk traglaakh", with the first half meaning "ugly fiery wet emptying things", and the other "made from the loss of trag" in the dead language of Iruaric. Trag is a different pronunciation or phoneme in the transliteration of the language out of its glyph form, with the missing vowel as a glottalization, implying the Traag were named to mean "cave dwellers."
Behind the Scenes
The Traag were never actual creatures in the game, but their existence on The Broken Lands was implied by the original name for the magru. They provide a conceptual link in how the work of Uthex Kathiasas in fashioning extra-planar entities, "(a new source of) power given physical form", would have been corrupted toward the demonic by the subtle influence of The Dark Path. If the traag were one of the allusions to "The Dream-Quest of Unknown Kadath" in The Broken Lands, they would be the cats who sneak off at night to the "cryptical realms" known only to cats on "the moon's dark side." Still more specifically, they would be the "large cats of Saturn" who were allied with the wicked toad-things and almost-humans of the moon, who were servants of the "crawling chaos" Other God. The moon in this context refers to the one in the dreamlands rather than the waking world, where the "moon-beasts" represented by myklian obeyed a great demonic pharaoh "god of the outer hells."
The following is the bone pit of creatures the magru have stripped of all their flesh. The huge "unrecognizable creature" by implication is not a myklian, and must be something that no longer exists. The "deep layer" of bones owes itself to the process having gone on for the past six thousand years, and supports the idea the crystal dome is reincarnating the entities whenever they are killed. The bone pit along with the stalactites and stalagmites in the Dark Grotto may be an allusion to "At the Mountains of Madness", where a cavern is breached filled with ancient bones of unknowable predation (which includes the Elder Things, the destroyers of the telepathic race from "The Shadow out of Time".) It was similarly accessed through a relatively small crack and was formed long ago by trickling water. Both stories have shoggoths in those places.
[Deep Pit] A deep layer of old bones forms the floor of this deep pit. The high straight walls are rough and irregular, riddled with cracks and sharp protrusions of stone. Obvious exits: none. >look bones Bones of all sizes and shapes are collected here, ranging from the tiny skulls of common mice to huge thigh bones from some unrecognizable creature.
However, the bone pit itself is more immediately an allusion to the vast Vale of Pnoth below the "peaks of Throk" in the dream underworld, where the night-gaunts would leave their helpless victims. The huge cavern corresponds to the "vaults of Zin" which is thought to be connected to the monastery of Nyarlathotep on the plateau of Leng, which corresponds to the abode of Uthex in the hooded figures. The "huge thigh bones from some unrecognizable creature" refers to the enormous "gugs" who fed on ghasts in the vaults of Zin whose bones were occasionally encountered in the Vale of Pnath. The entrance to the vaults of Zin was a cave near a "sheer perpendicular cliff" that the narrator reached crawling through burrows entered from a "dim-litten plain whose sole topographical features were great boulders" which clearly corresponds to the Jagged Plain.
It might refer further to the Great Abyss in the dream underworld which connects up to Ngranek, the home of the gods before Kadath, whose passageway is guarded against trespassers by the night-gaunts. The narrator was kidnapped from there to the Vale of Pnath by night-gaunts, passing over "nethermost grottoes." However, the huge cavern also makes allusion to being the Enchanted Wood with its fungous spires, parallel to the Graveyard forest, since the huge stairs and bas relief correspond to the tower of Koth. (Ghast tombstones were lichened monoliths.) In the Lovecraft original the tower represents the exit of the dreamland underworld to the surface, but here the wood is in the underworld and the huge stair instead is leading up to the portal into Kadath. It could also be interpreted as the Gate of Deeper Slumber. Interestingly, the word Pn'oth would itself translate as "lore mountain" out of Iruaric and Seoltang, and likewise Pn'Tairken is remarkably the Iruaric for the Loremaster naming of The Broken Lands. Most of the stories The Broken Lands uses include the "Pnakotic Manuscripts", which were made by the trans-temporal telepathic race, or possibly by the Elder Things and passed down to Hyperborea.