This article is from the X-Men Comic Books FAQ, by Kate the Short (firstname.lastname@example.org) with numerous contributions by others.
The Siege Perilous is a large, brooch-like magical gemstone that Roma, a
powerful mystical entity, gave the X-Men after the Fall of the Mutants
storyline (UXM #229). The whole idea of the Siege was that one could
send people through it, who would be "judged" by some unknown, higher
power (possibly Roma herself), and then be given a second chance at life
if found worthy, so they could try and correct their evil deeds, so to
This interesting way for heroes to rehabilitate their villains lasted
for about one storyline, the original encounter with the Reavers (UXM
#229) in Australia, until the press of crossovers and editorial
interference kept Claremont from using it much more than he did.
Claremont was, believe it or not, reportedly planning on spending well
over a hundred issues of the X-Men based in Australia, and thus his
leaving during the X-Odus could be viewed as somewhat of a relief,
depending on what you thought of the Oz-Men. Indeed, pretty soon the
Siege became an escape route for the X-Men from their enemies, as a
series of vicious, horrible encounters ended up with the X-Men believing
themselves better off reincarnated through the Siege than captured by
their enemies. Having Psylocke control their minds so they thought it
was a good idea (it was mainly hers) helped also. She had a vision in
UXM #250 of the remaining X-Men being turned into cyborgs and left for
So most of the X-Men popped through, and ended up, mostly with amnesia,
all over the world, mostly living lives they felt mostly "better" in
than superheroing--for the most part. The Siege was then captured by
Donald Pierce, who destroyed it (UXM # 251).
The X-Men who went through the Siege were:
* Rogue: Pushed through it by Dazzler (UXM #247). Reappeared in the
Outback in #269, then went to the Savage Land with Magneto who
freed her of Carol Danvers.
* Dazzler: Convinced by Betsy in #251, reappeared in Malibu and found
by Guido in UXM #260.
* Colossus: Convinced in #251, reappeared in Soho as Peter Nicholas,
artist, in UXM #259.
* Havok: Had doubts, but Betsy coerced him psychically in #251.
Reappeared as a Genoshan prelate in UXM #270.
* Psylocke--Went through #251. Reappeared in #256, only to become a
Storm did not go through, as she was captured by Nanny in #248 (although
they thought Havok killed her). She was de-aged, paired with Gambit in
UXM #266, and then re-aged to adulthood in #272.
Wolverine was left to bleed to death in the Australian wilderness in UXM
#251, where he was found by Jubilee.
Longshot had left voluntarily in #248 to find himself.
The original Siege Perilous, by the way, where Claremont got the name,
was the seat at the Round Table of King Arthur which had letters on it
that prophecied that only the "purest and greatest" of all knights would
sit there, who turned out to be Galahad. See the appropriate Malorian
(and other) sources for more on King Arthur, Galahad, and the Grail
Quest. Siege Perilous literally means "the dangerous seat."