Here is the history of Shandalar, the moving plane, featured in M-201X core sets and elsewhere.
"Shandalar is a rogue plane, drifting through the multiverse instead of retaining a steady position or course. It is a relatively small plane and incredibly rich in mana. The magical energy is so prevalent, that it all is sentient, and the common people use minor spells as an everyday convenience.
Shandalar was the setting of MicroProse's 1997 Magic: The Gathering computer game." -mtgsalvation wiki.
Shandalar was the plane used to enable the mending of the Ice Age by Freyalise, (see the book: Shattered Alliance) to the rest of the Multiverse, where Lim Dul was taken once Shandalar came close enough to The Shard of the 12 Worlds by Leshrac, where he also interacted with Tevesh Szat.
Here is the basis of the Microprose story, as well as the 2 part comic miniseries: http://wiki.mtgsalvation.com/article/Shandalar
M13: Now, recently, two planeswalkers visited Shandalar, and battled, one on a demonic mission to get the Chain veil; the other now hunting her. They were Liliana and Garruk and they fought in the Onnake Catacombs.
Liliana later returns, to try to deposit what she has taken from the Onnake.
Now, we have a new tale from the wandering plane, of Sentos, and his choice not to execute a man, who was once the False King. And his meeting with a Xathrid Gorgon.
We also know that Talrand is from Shandalar, and his reign begins with his tale.
M14 updates: Shandalar has a unique brand of slivers, found out from this report from Hastric, Thunian Scout.
A side story possibly on Shandalar, about the "Blessed life".
M15 update: The Bard and the Biologist