In The Lost Vault of Tsathzar Rho, a defenseless village asks the characters to slay an out-of-control ogre. Sounds easy enough. But the ogre, who used to be nothing more than a nuisance, has become crazed and psychotic. When the characters arrive at its cave, they find a subterranean portal has connected the cave to a much larger underground complex. Something in that complex has transformed the ogre and many other local creatures into fiendish marauders. In fact, it’s the lost vault of Tsathzar Rho, an ancient wizard and prophet of the Outer Gods, who are gathering their foul minions for battle.