"When the moon rose and the apparition of Amber came faintly into the heavens, stars showing through it, pale halo about its towers, tiny flecks of movement upon its walls, I waited ... waited on the highest crop of Kolvir, there where the three steps are fashioned, roughly, out of the stone...
"When the moonlight touched them, the outline of the entire stairway began to take shape, spanning the great gulf to the point above the sea the vision city held. When the moonlight fell full upon it, the stair had taken as much of substance as it would ever possess, and I set my foot on the stone.
"...If I looked too hard at any portion of the stair, it lost its shimmering opacity and I saw the ocean far below as through a translucent lens..."
'Sign of the Unicorn', Chapter 10
Still there every full moon, for a few days each month, as it was before the Primal Pattern was redrawn, reached by the place's equivalent of Amber's Great Stair, which forms from the three rough-hewn steps on the highest outcrop of Kolvir. By daylight, these look less like stairs, and more like jumbled rock.
As before, Tir contains visions and portents, usually more disturbing than enlightening, which still fade to the clarity of remembered dreams within hours of returning from it. The elders have said that it has changed somewhat since Patternfall, but not in any way they can put their fingers on.
The Pattern of Tir-Na Nog'th is somewhat different from the other Patterns:
"This Pattern, I noted, glowed with a paler light than the one in Amber - silvery white, without the hint of blue with which I was familiar. Its configuration was the same, but the ghost city played strange tricks with perspective. There were distortions - narrowing, widenings - which seemed to shift for no particular reason across its surface, as though I viewed the entire tableau through an irregular lens rather than Benedict's Trump."
'The Hand of Oberon', Chapter XIII
Magic does not generally work in Tir-Na Nog'th above the level it does in Amber. The exceptions to this are the occasions where it seems to fit into whatever vision is currently taking place. Even then it can be working at wherever the vision is, but not elsewhere in Tir.
There are two trails up to the peak of Kolvir, a rugged one which goes directly up the crest of Kolvir, and an easier one which winds around the peak of Kolvir to the south.
In order to protect the Tir Pattern, King Random has had several guard posts built at points up the two trails to the peak of Kolvir, the highest next to the steps themselves. These guards have similar orders to those around the Pattern room in Amber. They use Trumps to travel to and from the castle.
The lights of Rebma can be seen below the sea from Tir-Na Nog'th.
In The Last Enemy game, Tir-Na Nog'th is a shifting kaleidoscopic mirror of all of shadow. There is nothing 'behind' it. The ghosts within it are essentially random scenes from shadows which reflect the viewer(s) in the same way that shadow is a 'reflection' of Amber. In terms of its physical structure, it is effectively a hologram, projected onto a patch of sky defined by the geometry/arrangement of the Patterns and moonlight. Anyone flying through that region of the sky might feel that there was something strange and Real there even when Tir-Na Nog'th is not visible.
The only actual inhabitant of Tir-Na Nog'th is Ossian, the twin brother of Oberon and the King of Tir-Na Nog'th.
He can sometimes be found in the throne room of Castle Tir-Na Nog'th. When he is present the doors to the throne room seem paper-thin, gossamer-like, and the room itself insubstantial. Gothic arches and columns are visible to each side of the room, and a thirty foot long bed stands on the dais where the throne should be. In it lies Ossian, a thirty foot-tall, thin, beardless man with a distinct resemblance to Oberon, sleeping peacefully, his long white hair spread out on the pillow. Above him is a huge stained-glass window showing an hourglass about half spent. Two normal-sized ravens sit on the bedposts, looking directly at visitors in that way that Tir-Na Nog'th visions tend not to.
Tir-Na Nog'th has no close shadows, although the various sky-cities found in shadow are obviously reflections of it to some extent.