First, summon a unit. Summoning units requires mana. Units deployed on the board will summon warriors to the fight when a new wave is starting. When you kill enemy warriors and pass out offs, you earn mana. Spend some mana now to increase mana generation at each cut off. It's more profitable to spend mana on upgrading units to increase damage. Upgrade archers and prepare for the next wave of battle. The upgrading extends to cover the warriors appearing with the next wave. Merge two characters of the same type. As you can see, the results are random. Eight heroes of the first rank have merged into one hero of the fourth rank. A warrior summoned by such a unit is string, but hits weaker than the eight warriors of the first merge rank. When merging up to the third rank, the power of the warriors is retained. From the fourth rank onwards, some power is lost, but some units summon more warriors.