Do other Amberites have the ability to interact with the phantasms of Tir-na Nog’th, via some other artifact or technique? Is the power that Corwin has in Tir unique?
Referencing back to this entry, Tir, City in the Sky.
Corwin has two advantages in the scene: first he is of the line of Faiella and that blood has an affinity for moonlight and sky. Second, he has Grayswandir, the nightblade, which has ancient connections to Tir.
Corwin compares Tir to a casting of cards: a place where inspiration might strike. Interaction with the visions is not required. IMC, the blood of Faiella can get responses. Tir also allows access to arcane planes that Amber is protected from. In this latter sense, the sword has some special abilities.
IMC, Oberon has little to do with it. He does have something to do with Grayswandir going to Corwin. Oberon did not discover Tir, Faiella did.
Interactions might happen through sorcery, blood of Pattern, certain ancient powers that existed before Pattern and other rare forces.
Tir provokes emotional connections and jumbles sensations if you are susceptible to its influence. It is also usually a private experience where you can react plainly without artifice.
Why does one wake from a dream in tears or afraid? There are as many cases as there might be dreams.