Build a lair and treasury immediately. Open up the top portal but ignore the bottom one. Use the free magic door to stall the first wave until you get a dragon. Possess the dragon and use it to kill the first 2-3 waves of thieves/archers.
After that you should be fine. The gems and the ludicrous amount of imps you're given is more than enough to afford training most of your creatures simultaneously. Eventually you'll be able to just dump all your monsters on the parties that show up.
If you still have trouble, you can just plop a lava trap in your one entry point and in the hallway to the gems. Stick a few boulders in your hallways, bridge the lava trap and let the heroes all kill themselves.
Looking at the script, a single possessed dragon would be able to deal with all parties up until the end few;
Samurai would be a pain due to perma-freeze shenanigans and Witches would be easier to just Lightning Strike to death.Code:CREATE_PARTY(ZEHN) ADD_TO_PARTY(ZEHN,WITCH,10,1000,ATTACK_ENEMIES,0) ADD_TO_PARTY(ZEHN,WITCH,9,1000,ATTACK_ENEMIES,0) ADD_TO_PARTY(ZEHN,WITCH,9,1000,ATTACK_ENEMIES,0) ADD_TO_PARTY(ZEHN,WITCH,9,1000,ATTACK_ENEMIES,0) CREATE_PARTY(HARA) ADD_TO_PARTY(HARA,SAMURAI,8,1000,ATTACK_DUNGEON_HEART,0) ADD_TO_PARTY(HARA,SAMURAI,8,1000,ATTACK_DUNGEON_HEART,0) ADD_TO_PARTY(HARA,SAMURAI,8,1000,ATTACK_DUNGEON_HEART,0) ADD_TO_PARTY(HARA,SAMURAI,8,1000,ATTACK_DUNGEON_HEART,0) ADD_TO_PARTY(HARA,SAMURAI,8,1000,ATTACK_DUNGEON_HEART,0) ADD_TO_PARTY(HARA,SAMURAI,8,1000,ATTACK_DUNGEON_HEART,0)