Walking the Pattern is not an easy task. There is a resistance that slows the walker, as if he is wearing lead boots that get heavier and heavier with every step. During the ordeal, the walker passes through several points of extreme difficulty called "veils"—The First Veil, the Second Veil, and the Final Veil. These points represent intense surges in this fierce resistance; however, "breaking through" a Veil causes the resistance to let up a bit.
Once at the Pattern's center, the walker has acquired the power to walk in Shadow. As well, being at the center gives him the opportunity to command the Pattern to send him anywhere he wishes--across the room, back up to Amber Castle, across the world, to another Shadow world, here on Earth, etc.
During the series, it is revealed that Amber itself is but the first "Shadow" of a Primal pattern located when the Unicorn of Order leads Corwin to a previously unseen location. The Primal Pattern is guarded by a dragon/Wyvern type creature that apparently has also been placed there to guard Dworkin (previously thought deceased), as Dworkin has, at this point, lost much of his mental faculties. This Primal Pattern is damaged prior to the events of Nine Princes In Amber (by the spilling of Amberite blood on the Pattern - the blood of Martin, son of Random, Oberon's youngest acknowledged child.) Oberon attempts to repair the Pattern, although he realizes the process will kill him. Brand, whom Dworkin acknowledged as his most apt pupil in study on the Pattern, suggests that such repair may not be possible. Brand also suggests when Corwin is inscribing his own Pattern that there cannot be two such centers of order in the multiverse, and that it is necessary to destroy Corwin's Pattern before he can inscribe his own. However, Oberon successfully repairs the Pattern, and it is seen to coexist peacefully with Corwin's Pattern - possibly because both are merely reflections of the Pattern in the Jewel of Judgment.
It is implied that nobody could successfully repair the damaged Pattern perfectly, or reproduce it as it originally was: and that their own personality would be inevitably imprinted on it in the attempt. A fact accepted - and desired - by Brand, who wished to destroy the Pattern outright (and Corwin's, as well) and re-create a new Pattern in his own image, with himself as architect of the new Universe: and a fact either not known or misunderstood by Corwin, who attempts to faithfully recreate the old Pattern (after Brand deceives him into believing Oberon to have failed in his attempt to repair the original) only for his new Pattern to not only evolve differently but eventually resist the attempts of the successfully-repaired Original Pattern to incorporate it. It follows, from this (and from the fact of Corwin's successful creation of a New Pattern, in which he did not die) that it may not have been necessary for Oberon to die in repairing the Old Pattern: and thus that, since Oberon did indeed die, he may even have done so willingly (and known in advance that this was necessary) as a way to avoid imprinting his personality on the Old Pattern at its re-completion. At any rate, after its repair, the Old Pattern (when displaying sentience) does not appear to display any characteristics of Oberon's personality.
In the Merlin Cycle, the second series of five novels in the Chronicles, the Pattern is shown to be sentient. It is able to manifest itself at any point in shadow, and teleport others without their consent. It is also able to create Pattern ghosts, artificial versions of any person who has walked the Pattern.
The Jewel of Judgement is revealed to be the left eye of the Serpent of Chaos, stolen by the Unicorn at some point in the very distant past. It eventually ends up serving as a replacement eye for Coral, allowing her to see the "clear, cold lines of eternity".