Start by claiming the dungeon you're in, quite soon you'll be attacked by heroes and they will keep coming for a while. However, among the starting rooms is a prison and the torture room is the first thing you'll research and you'll get enough time to patiently convert all the heroes to your side. I however chose to go with a skeleton army this time and just converted the healing heroes and lvl 10 thieves. You'll get some gems but the only limiting factor is that you can't build a treasure room on this map.
After a while the parties stop coming, and apparently this is the time to hunt for the remaining hero pockets on the map and feed them to your prison. When you've killed everything the final party will come shortly, about 25 mid-level heroes that will try to kill your 150+ lvl 10 army.(There's lot of increase level specials on the map).

In short, a very average hero invasion map, it works fine but from the midgame onward too easy because of the overpowered rooms.