Synergies

When creating your formations, if you put 2 or more of a particular Race or Class together (with the exception of Demons and Assassins), you will receive a synergy bonus. These bonuses increase in strength with the more of that race or class you include in the formation, whether this is through increasing numbers, or adding new bonuses to the synergy bonus.

Demon Synergy
Demon stands out as an exception to the other Race and Class synergies, as it is based around have exactly 1 or 4 demon heroes in your formation to receive the bonus. Whereas for the other Races and Classes, and only need at least a specified value.

Assassin Synergy
While the Assassin Synergy operates in the same way, when you have 2 or more Assassins. Assassins also have a synergy bonus when there is only 1 of them in the formation, which is included with any number of Assassins.