A cut scene will begin. Seems the old Overlord wasn't dead after all. Now you have no minions or spells. This should be fun. Go down the stairs to the right. A cut scene will begin. Your mistress will damage the tower heart. Then you must fight several minions. You must fight something like 10 brown, red, and green minions.
After the fight you get your spells back. When you walk near the brown summoning pit a brown will pop out and join you. You also now have your brown minions back.
Grab a full load of brown minions and go through the hole the wizard made. Go through the arch on the right. Minions will pop out of the ground. Go to the right and up the hill. At the top of the hill is a wheel and the red minion hive. Have your minions turn the wheel.
Next have your minions grab the hive.
Protect the minions on the journey back to the spawning pit. Once the hive back in the spawning pit, grab 10 red minions. Go back to the first archway. Turn left and send the red minions to get the blue hive.
Grab ten blue minions. Go back to the same first archway. Go forward once through the archway. Have red minions turn the wheel. Cross the bridge and follow the path to the water.
Go to the green hive in the water and clear the minions from around it. When that is done, call blue minions in to grab the hive. Follow them back to the spawning pit. Woot! Now we have all the minions. Grab ten green minions. Go back to the archway.
Go to the bridge and cross over. This time go left and have the green minions clear the poison gas. To the left is a wheel. Have your minions turn the wheel.
Cross to the island and have your minions turn the wheel there.
Cross the bridge and go back to the spawning room. Get your usual load of minions. It's time to take the wizard down. Go back to the door in the area where the greens cleared the gas.
Enter the door to the final battle. As soon as the scene ends set a guard marker. The wizard will put up a colored shield. Send a minion of the same color to force him to drop it. The strategy I used was to wait for him to put up his green shield. Then sick your green minions on him. They do the most damage. It took three rounds of this method before he fell.
When the shield is dropped the wizard will drop to his knees. Attack him until he forces you away. Repeat until he dies.
The Wizard will be in the middle of area. Walk up to the Wizard and hit him with your weapon.