Much like , BoC is a two hour event with zero risk to your troops, subordinate cities, and resources. The main difference is that there are more buildings and no bosses. Points are awarded for holding buildings and killing enemy troops.
Important buildings that are not found in :
Constantinople is located at the exact center of the map and gives 5 points per minute held to the first person to hold it and 1 point per minute to subsequent reinforcers.
The Knight's Hall sends waves of troops to attack the team that does not hold it. Much like undead the waves are sent every few minutes. The main advantage to holding the Knight's Hall is that you can follow the lines of marching troops to locate the other teams cities.
Reward difference from :
BoC gives badges instead of research stones and Dragon Crystals. This is the only way to get Badges which are required to unlock the wonder and to upgrade . Besides this difference the rewards are exactly the same
Please read my guide on for basic tactics and a more thorough explanation of how battlefield events work: