Mine over Matter is like an X-terra event, minus the brand name. Off-road triathlon - swim, mountain bike, trail run. It takes place at the Kelso Conservation Area in Milton, Ontario.
Check out this awesome video of the 2010 race... this is a must-do!!!
I was hoping to get out there at least once to check it out, but it hasn't really come together, so I'm going in a bit blind. All I know is that there are some very long climbs on the bike course (goes up a ski hill) and it's two loops... I don't imagine the rest of it is flat either. Should be a good challenge.
I haven't had my "swimming mojo" this year, so I am doing the duathlon (trail run - mountain bike - trail run). I did a mock duathlon in training this weekend of similar distances just to get a feel for the transitions, it went well. Seems that I can go pretty hard on the first run without hurting my bike and second run excessively, so that will be the plan.