The new feature: Alchemy. Using this skill you can make potions. All you need is some plants (which grow only in selected locations), a recipe (you can discover it through experiments) and an Alchemy Toolkit (very rare item, but...).
There are several new monsters. They are not just the old monsters with better parameters, but also their behavior differs, notably Mountain Orcs and Goblin Warriors can use ranged weapons, forcing the player to develop new tactics.
Full change log:
Enjoy!