Slave Collar. . . unimaginable rage. . .

[HoneyBadger]

For a purely evil use, you can conquer a nation of hoburgs, recruit a bunch of their leaders, slave collar them, and then put those leaders on the front lines when your fighting jotuns, demons, hydras, etc. It won't help you win the game unless the other side picks up the collars, but it's fun (in a sick and twisted way) to watch them charge the enemy.

I won't go into uses involving summoned succubi, because most of those types of uses go on outside the boundaries of the game as intended. But I will think about them, and may discuss them with my wife.