The demo should contain all of the moathouse and its associated levels/dungeons. You are given a 2nd level party and a little bit of backstory o­n why you are there and it ends when you reach the very bottom of the moathouse.

IIRC the party consists of a Monk, Fighter, Cleric, Bard, and Wizard. All the non moathouse maps have been stripped so there is no worldmap travel, all the spells should be there, all the monsters that don't spawn o­n the moathouse or in the moathouse random encounter tables have been removed, all the non moathouse music has been removed, and the existing moathouse music has been recompressed (to make it smaller). Most of the movies have been recompressed to be smaller, and lots of the sounds (especially spell sounds) have been compressed to make them a lot smaller (at the expense of quality and a tad bit of performance the first time they are loaded).

The last time I measured it weighed in about 220meg, its mostly all the damn spells and spell effects, not to mention plenty of monster art.