Monsters never miss in melee and spells never fail. Monsters get critical hits in melee more often. Players get critical hits less often. Ball spells initiated by the player will damage the player if he is in their sphere of effect. Selection of shopkeepers is biased towards those with the lowest purses.
Shopkeepers never rotate.
Shopkeeper greed is increased by 20. Shops are less likely to stock piles of an item and piles will be smaller. Your home may be robbed if you do not visit it at least once each day. Terrains that can damage the player will do twice as much damage as normal. The game occasionally creates both invisible walls and walls which seem normal but are passable by both the player and monsters.