World of Xeen is a combination game of Might and Magic IV: Clouds of Xeen and Might and Magic V: Darkside of Xeen if both games are installed on the same system.
The combined game contains the full content from both games and adds an epilogue quest requiring to overcome 8 new dungeons.
Indeed, after Sheltem has been defeated, the Guardian Dragon Pharaoh summons the party of adventurers to request them to assist in the achievement of the Ancient experiment to convert the nacelle flat world X.E.E.N. into the artificial planet Xeen.
After the party has completed all of the 8 dungeons, they witness the Unification Ceremony where all of Xeen's inhabitants are invited in which the Guardian Dragon Pharaoh weds Prince Roland of the light side and Queen Kalindra of the dark side as Prince Roland inserts his Sceptre of Temporal Distortion into Queen Kalindra's Cube of Power on the Altar of Joining which completes the conversion of the flat nacelle world X.E.E.N. into the artificial planet Xeen.