Top Cow and Marvel have had a very successful run of company crossovers through the years. I think they've all been pretty fun, well drawn, and overall worth the experience. I think it all started with "Devil's Reign" back in 1997 which saw Marvel's Mephisto going to the Top Cow Universe to steal souls so he could become more powerful and rule over the Marvel Universe. While the premise sounds a little weak, the crossover was fun. This new crossover event is a 3-issue miniseries called Fusion where we get to see the Avengers and Thunderbolts from the Marvel Universe and Cyberforce and Hunter-Killer teams from the Top Cow Universe come together for a reason that has not been made clear by the end of this first issue.