Heroes in Combat
After the disappointment of Heroes IV, many people wanted to see heroes return to their former role on the sidelines. The result is a combination of these aspects. Some heroes stand back from combat to cast spells and enhancements, while others are actually able to participate and enter the fray. The system has not been tested yet, so it is difficult to tell whether this will be successful or not.

Heroes on the Adventure Map
All heroes/armies will now leave a trail wherever they go. The depth and longevity of the trail is determined by the size of the army. Heroes will be the only mode of transport (apart from the Caravan) and there are now different ways of going about it. The Inferno Hero, for example, is too big to fit on a horse, so he walks around the Adventure map. Other heroes have respectively fitting horses.

Heroes in the Town
The idea has been thrown around that you will only be ale to recruit one hero per town. This is unconfirmed information, but it would prevent players from buying 5 heroes in one week and ferrying them all around the map. It also encourages players to make use of caravans more, now that creatures cannot explore by themselves.

Thanks to ThE_HyDrA for creating and looking after the Heroes 5 section of Age of Heroes!