by Akden
As mentioned earlier, for the most part the factions are mainy associated with the backstory. You can find some of that fluff by google searching for "Thormun's Journal." There are a few unit bonding abilities that specifically reference factions (Sacred Band refers to a warlord that follows Einar, and Ornak benefits units that follow Utgar, for example), but most bonding is dependent on the type of unit (ie. champion, beast, warlord, etc.). Obviously, the generals have specific themes associated with them (Einar is mostly historical eras, Vydar has more robots and agent types, Ullar has an elf/fantasy theme, etc), but there are no rules preventing you from combining different units from the various generals.In regards to tournament play, a lot of that depends on your location. I just went to a tournament in Maryland with more than 30 participants, and there are fairly active scenes in various regions. I realize that Heroscapers.com is a lot to take in, but there is a forum for event postings: http://www.heroscapers.com/community/forumdisplay.php?f=11
Also, various conventions have organized tournaments, particularly Gen Con, which had 12 or so large events. I'd recommend looking into that, if you can make the trip. There is also the opportunity to play Heroscape online using Skype, which is pretty amazing and could open up opportunities to play with a variety of opponents: http://www.heroscapers.com/community/forumdisplay.php?f=108
Heroscapers is full of great resources, including the Books, which is a collection of all the units: http://www.heroscapers.com/community/showthread.php?t=8099,
army-building threads: http://www.heroscapers.com/community/showthread.php?t=25409, and strategy articles: http://www.heroscapers.com/community/showthread.php?t=10693. It can be a little intimidating, but there's a lot of great stuff there, and it's a great community. If you have the time to browse, I'd recommend trying it out.