They go where you want them to go, but as there can be up to 50 of them in a group their personality and class will dictate what they do when they get there. Lead your faithful followers into a pumpkin patch and they’ll carve the pumpkins into helmets (upgrading themselves in the process). Send them into a herd of sheep and it’ll be a case of lambs to the slaughter as the goblins fall on them. Force your minions through the door of a house and you’ll hear whacking and fighting from within, and they’ll come out again with loot for their master and probably wearing pots on their heads (another upgrade).
Controlling your minions is endless fun, and their class strengths and weaknesses come into play solving puzzles. For example, the red imps, who spit balls of fire into their hands and lob them at the enemy, are also immune to fire, making them perfect for sneaking through flames to trip switches.
Overlord’s fallen fantasy world is suitably twisted to match its subject matter: the heroes who killed your earlier incarnation have themselves become corrupt and cruel, the lands around them warping to match their decay. They’re based around the seven deadly sins: the elven king has become so slovenly, for example, that he’s sprouted leaves and become a tree. His massive roots form the basis of the level: you travel along them to the point of his power.
Amid all the minion manipulation, it’s easy to lose sight of the Overlord himself. He’s a powerful fighter, his attacks based mostly in magic and melee. As he grows in power, and his minions gather the lost remains of the Dark Tower, he’ll take over the lands, people and places. He’ll even get a jester, who’ll announce his arrival spewing the litany of evil deeds the Overlord has accomplished, until you get sick of it and kick him. Just how evil do you want to be? It's up to you, really.