Brotherhood

Brotherhood is the 18th level in Dungeon Keeper 2, located in Cherry Blossom.
This mission will be long but fortunately, all three Keepers, including the powerful Nemesis, will not actively assault you unless provoked. It would be wise to use the time to build up your dungeon and train up your creatures to very high levels. Then, you should kill them off one by one.
Despite the objective stating that you must defeat Faust and Fabius too, Nemesis' defeat at your hands will win you the level regardless of whether they still stand.
== Strategy ==
This level is fairly stable, and can be played without much fear of continued enemy attack so long as you don't breach their defenses. Keeping the dirt barrier in front of Nemesis's northward facing magic door intact will result in him being entirely dormant and keep your minions from wandering into his territory. 
The second portal available to you to the west of your heart will provoke 3 hero incursions from the nearby hero gate. 2 trios of elven arches, then 1 final incursion of 2 royal guard and 1 knight. This can be a good chance to convert heroes so they can be used to pray at temples.
The Hero fort to the east can be easily dealt with by bottlenecking the area with gas traps, boulders, and sentries. But the real prize are the dwarves. They can tunnel through enemy fortifications with relative ease, so its best to convert them and keep them locked away until needed. Monks and fairies are best used to pray at temples for extra mana generation.
In the beginning it may be useful to abuse the Temple's sacrifice system. By building a guard room, torture chamber, workshop, and a large hatchery, you can attract the creatures needed to gain as many Black Knights as you want. Training a sizable force of them to level 8 almost assures victory. Creatures you don't want in the beginning can be either thrown in the prison and slapped, giving you corpses for vampires which can be sacrificed for bile demons (and from them rogues for more black knights) or more skeletons which can be used to continuously pray at temples.
Fabius is the weaker of the two brothers, and tunneling next to his lair wall and building traps to support your invasion force is a good choice. The same can be done with the north facing wall of Faust's casino.
Nemesis can simply be rushed once you have destroyed his sons and leveled up all the minions that come from their portals. However if you destroy the east, west, and southern outer defenses and place sentries alongside his walls, then collapse the walls at once [Dwarves, either captured or acquired by sacrificing goblins come in handy here,] and Nemesis will not be able to focus on every point of attack, allowing you to claim much of his dungeon with relative ease. Possessing a high level rogue before this tactic to clear out the multitude of traps yourself can speed this up, and reveals any hidden traps your minions may fall for. Summoning Horny to rampage through his dungeon will severely reduce the danger.
If you wish to slay Nemesis without killing his sons, tunnel along Faust[the yellow keeper]'s western portal and use bridges to accomplish the same strategy above. A door can be used to control imp and minion involvement, and a high level rogue clearing out Faust's sentries makes things a lot less stressful.
==Breakdown==
== Trivia ==
The AI for Faust and Fabius at first appear to be hostile, and even the Mentor suggests the pair squabble often. However, the pair do not attack, or claim each other's land or that of Nemesis. Should the player unleash captured heroes or rebelling creatures into Nemesis's Dungeon Heart room and they slay him, the level's To-Win prerequisites cannot be met, and the level will become unwinnable.
As mentioned, defeating Nemesis is enough to win the level. If one stays on the level after his defeat and defeats another Keeper, 
Slaying Nemesis without destroying Faust and Fabius's Dungeon Hearts results in an alternate victory speech from the Mentor. 
Keeper Nemesis has Chicken Spell, to make up for the lack of his Summon Horny.