Use the tower heart and choose Heaven's Peak city as your destination. Get your minions quick. The raiders will start attacking you seconds after you arrive.
There are three of the floating creatures in this section. There is one of the blue and two of the red creatures. Set up shop and kill them with your minions.
Go through the archway that is across from the teleporter. In the next section of the city, you will run into Kahn. The way I killed Kahn was to have 20 reds and 15 green minions. As soon as the cut scene ended, I guard marked the minions and run down the stairs. He lasted like 10 seconds maybe a bit more.
Kahn will run after he takes some damage. Follow him into the next section of the city. Follow the only path. As you cross the main gates, a cut scene will begin. As you come around the end of the path on the wall, Kahn shows up again.
If you can get your minions to spin the wheel it will cut off the raiders from spawning during Kahn's fight. After so much damage he leaves again. I used same tactic.
Follow him out of the back right corner of area. Follow this path the building where the townspeople turned in to zombies.
There is summoning pits of all colors to the left of building. The way you want to go from here is to the left. Kahn is waiting at the Halfway to Heaven Inn. There are also some of the floating creatures near the inn.
When you get to the Inn guard marker, put your minions near the Inn entrance. I just ran around the area bringing Kahn close to my minions. He killed quite a few but they took him down a bit.
Once Kahn is on his knees hit him with your weapon.