Map of Ulthuan; the Annulii Mountains form the central, mountainous spine of the island-continent.
The Annulii Mountains are a range of titanic, cloud-piercing peaks which separate the inner and outer High Elven kingdoms on the island-continent of Ulthuan. The highest valleys and plateau of this region disappear into a strange, glittering mist of raw magic so strong it becomes visible even to those without the witchsight.[1a][2a]
Within this realm the stuff of dreams and nightmares can coalesce from the very air. The sun is never visible, it is eternal twilight. Time flows strangely and travellers become lost for years although they think they have been walking only hours. Even the use of magic becomes unpredictable in the mountains. This unstable region of Ulthuan has a strange, other-worldly quality more akin to the Realm of Chaos than to mortal lands.[1a][2a]
The Annulii Mountains are riven with magic because Ulthuan itself acts as a focal point for the winds of magical energy which blow across the world of Mallus from the Northern Wastes. These drifting energies are drawn to Ulthuan, like water in a whirlpool, forming the Great Vortex. In this way, Ulthuan drains magic out of the mortal world and prevents the tide of it overwhelming everything and turning it into a seething realm of Chaos.[1a][2a]
The Annulii Mountains are near impossible to cross save by certain passes and tunnels guarded by massive fortified gates. Many wild and evil creatures are spawned in the mountains or drawn there on the Winds of Magic, taking shelter in the crags and catacombs. For the most part they are confined there by the same great spell which draws magic to the Great Vortex, but some things manage to find their way down to ravage the lands below. Griffons, Chimerae, and other monsters find their way into the hinterlands of the island-continent's Inner Kingdoms where they are hunted for sport or captured as war mounts by the High Elves.[1a][2a][3a]
So few passes breach the near-impenetrable mountains that most communication between the inner and outer realms of Ulthuan takes place by sea. Thus, the Inner Kingdoms are mostly unspoiled wilderness, covered by huge, ancient forests or grassy, rolling plains, utterly free of the stamp of habitation and civilisation.[1a][2a]
No Elf has ever scaled to the very summit of even one of the Annulii's peaks and spoken of it, but legends abound of an otherworldly realm beyond the clouds, where ancient gods hold court.[3a]
It's noted that upon reaching high enough, the wind becomes charged with pure magic, bearing Great Eagles aloft with minimum effort. Warm air from the Inner Kingdoms rises from the eastern flanks of the mountains to be met with a cold barrier of wind blowing inward from the sea. Mingled with the raw, powerful magic, the resultant thermals make racing through the sky an exhilarating experience, though the mighty avians seemingly care little for the sensation.[4a]