Your favorite hero...

They are summoned depending on the hero's level, so usually no more than 20, a maximum of 30, and only after the entire squad is defeated, i.e., usually at the end, and most often you don't even use them.

I like to develop very quickly, and in the beginning, the opponents are only neutral creatures. If you plan the battle well and avoid losses, the ghosts summoned from the undead are very helpful here! :)