I am going to be taking over the role of Dungeon Master soon, with a group of players that have leveled from 1 all the way up to epic tier. The characters will be level 21 at the start of my campaign. I've asked each player to choose their epic destiny a little early so I have time to work all of them into the story.
One is getting me stumped though: World Tree Guardian.
The epic destiny description has a little information about the World Tree and why a character would choose to defend it. But I am struggling to work that storyline into the campaign path we have been following. We are running the WOTC published modules dealing largely with Orcus and the Raven Queen.
So, where can I find more information about the World Tree and its influence on Toril? What books/magazines/etc have published more information about it?