Crystal

I don't remember exactly, it was a long time ago, but I think in the first week I cleared out the monsters at the top, took the Spirit of Despair artifact and a shield that gives +4 to everything, and also leveled up Expert Earth. In the second week, I attacked the horde of dendroids at the bottom with a horde of gremlins (with a few golems and gargoyles) :D. Although there might have been a few more mages.