I scanned the the first four pages and couldn't find anything related to this so I figured I would start a new thread.
I read that my character in Prophecies can take a mission to go to the other campaigns after reaching Lion's Arch. Can I actually complete all of the campaigns with one toon and have it count for HoM or do I need to start a new toon for each campaign for it to count?
As mif said, you can do all of the campaign missions on one character. But many secondary quests are limited to characters of a certain campaign, however those aren't needed for HoM.