On many message boards people have questions regarding the topic and often facts seem to be mixed up or entirely false. Listed below are the most popular misunderstandings with short explanations why they do not work.
1) The X-Men were resurrected in Dallas by walking through the Siege Perilous.
Wrong. The resurrection happened in Uncanny X-Men (1st series) #227, but the crystal was only introduced in #229. What might have added to the confusion here is that in #227, the X-Men sacrificed their lives for Forge to use their essences in a magical spell to seal a gate to the Adversary's dimension. Later Roma in her Starlight citadel pulls the X-Men's essences out of that gate. However this "gate" is something else than the Siege Perilous.
2) The X-Men gained the "technical invisibility" by walking through the Siege Perilous.
Wrong. The invisibility is mentioned for the first time in Uncanny X-Men (1st series) #229. As said above, at this time none of the X-Men had yet walked through the crystal gem. Roma explained that the invisibility was a side-effect from her resurrection, as the mutants’ lifelines had been broken and they now in a sense stood apart from life. Her exact words to describe the technical invisibility were: "You cannot be detected by any agency other than yourselves -- living or mechanical, magickal or scientific -- neither being nor power, nor enchantment. You may be seen by the naked eye -- and by the devices of this place, your new home -- but that is all." This applied to the X-Men from the Australian era, namely Storm, Wolverine, Colossus, Rogue, Psylocke, Longshot, Dazzler, Havok and their ally Madelyne Pryor.
3) Storm emerged from the Siege Perilous transformed into a child.
Wrong. Nanny and the Orphan Maker were responsible for Storm's condition. The confusion was caused by the fact that the juvenile Storm was naked and without memory in her first appearance and it was only revealed fourteen issues later what actually had happened to Ororo.
In Uncanny X-Men (1st series) #248, the remaining team (Longshot and Wolverine had left to deal with personal problems) was attacked by Nanny and the Orphan Maker. Storm tried to follow their aircraft but was captured by some metal tentacles as Havok used his plasma beams to blast the ship out of the skies. At the crash site, the team found Storm's scorched, dead body. Much to the reader's surprise, the child Ororo debuted a few issues later in Uncanny X-Men (1st series) #253. She appeared in Cairo, Illinois during a rainstorm.
Uncanny X-Men (1st series) #267 finally revealed that, off-panel, Storm had already been pulled into Nanny's ship where a life-model decoy of her was created. When Havok blasted the aircraft, Nanny escaped with her captive in a second ship, while the X-Men found the LMD at the crash site, believing their teammate dead. Nanny tried to bind Storm to herself by reducing her to childhood, but Ororo's will was too strong and she escaped during the process, though without the memories of her adult life.
Storm undergoing a fake mutate process in Genosha during the X-Tinction Agenda restored her back to adulthood.
4) The X-Men lost the "technical invisibility" by walking through the Siege Perilous.
Wrong again. Only five of the eight people in question (Madelyne died during Inferno) ever walked through the portal. So by all means Storm, Longshot and Wolverine should still be "invisible." Additionally, even after the de-aging, Ororo could not be recorded by technical devices. Finally, the other five have all been reported to still be invisible at one time or the other after emerging from the crystal.
5) So, Roma gave the X-Men three different, independent gifts: Resurrection, Technical Invisibility, Siege Perilous ?
Yes, sort of. Actually the invisibility was first named a side-effect of the resurrection. However, though the invisibility is no longer there, the eight X-Men are clearly still alive, so these two also don't seem to depend on each other.
6) So what became of the invisibility? When and how did it end?
This is a dangling plotline left open when Claremont left the book in 1991. Since then, it has been forgotten about. The most logical theory up to date is related to Excalibur's lighthouse. As revealed in Excalibur (1st series) #49, the lighthouse was a nexus place simultaneously existing on every Earth through the multiverse. In Excalibur (1st series) #50, Meggan imploded the lighthouse, and by doing this damaged the magical matrix of Otherworld where Roma’s palace is situated. As a result of this, long-term-spells like the X-Men’s invisibility could have dissipated.
However, the X-Men are first seen on video screens again in X-Men (2nd series) #1, which was released a few months prior to the Excalibur arc in question. So for this theory to work, Excalibur (1st series) #50 needs to take place before X-Men (2nd series) #1. Considering that Excalibur (1st series) #46-50 is a tight storyline, all happening in a single day and there was a time gap of a few months between Uncanny X-Men (1st series) #280 and X-Men (2nd series) #1 during which the mansion was rebuilt and Storm's hair grew back, this certainly could be the case.
7) Why did the Siege Perilous look like an amulet in Uncanny X-Men and a mirror in Wolverine and the X-Men?
The simple answer is that the Siege’s true nature is unknown. The Philistine seemed to believe it was conscious, so perhaps it takes whatever form it feels is needed to get the job done.
8) Why was Quentin Quire rejected by the Siege Perilous?
At the end of Wolverine and the X-Men (1st series) #31, Quentin Quire was about to be pushed through the Siege Perilous but in #32 he was chained up in the dungeon of the academy. It was revealed that he had been rejected by the Siege, something which hadn’t happened in thousands of years. The Philistine theorized that Quire had some higher calling or maybe he was not worthy enough for it. It would seem the first theory is the most logical one, given that a number of alternate futures depict Quire as being a host for the Phoenix Force and he even had a brush with it a few years back. The Siege could probably sense that Quire’s true destiny has yet to be fulfilled and that it is not his fate to be reborn. This also hints that maybe the Siege is indeed self-aware in some respect and is working alongside higher powers. However, these are only educated guesses and as yet solid reason has been given for the rejection.
9) What is the Siege Courageous and is it linked to the Siege Perilous?
During the Avengers vs X-Men crossover, the Phoenix Five, the members of the X-Men possessed by the Phoenix Force, used a something called the Siege Courageous. It is unknown what it really was and where it came from but its primary function was to open portals to allow the user to teleport anywhere in the world. No mention has been made of the Siege Courageous since the Phoenix Force left the mutants. Most likely, it was some technological device created by the Phoenix Five that was been subsequently lost with the fall of Utopia. Very little was revealed about the device and so far the only link to the Siege Perilous is their similar names.