Books like The black tower by Richard A. Lupoff

WELCOME TO THE DUNGEON It is a fortress where fantastic twists of time and space hold travelers from a dozen worlds captive. It is a prison in which cyborgs, swordsmen, eight-legged aliens, and beautiful women struggle side by side against their unknown captors. It is a trap within whose confines the known laws of nature and of science are suspended and the impossible is commonplace. It is an island in a dark and distant galaxy, a territory from which there is no return until an adventurer from Earth arrives, seeking his brother. From the heart of darkness to the edge of the unknown, this is the quest of Clive Folliot, explorer and hero! The return of a classic 'shared world' fantasy series created by Philip José Farmer, award-winning author of the RIVERWORLD saga. Plunging into a vast prison that spans a planet, Clive Foliott faces a fantastic world of dwarves, cyborgs and aliens unlike anything he has ever imagined. It is a multi-levelled collection of beings from the hidden folds of time and space. Trapped somewhere inside is Neville Foliott, Clive's twin brother and no creature in the Dungeon will stop Clive from finding him!

First publish date: 1988