If NWN2 had a weakness, it was the ability to rapidly rest after every battle, which let you fully heal and recharge all of your magical spells in about five seconds. Consequently, the game seemed a bit too easy. You weren't forced to make the hard choice about using a fireball spell or saving it for later on. Mask of the Betrayer has an interesting solution to this issue, and it's tied heavily into the plot.
The dark hunger that resides in you forces you to consume spirits to survive (the magical kind, not the alcoholic type). You become a spirit-eater, an entity that is feared in that region of the world—exactly how you find and devour spirits is something that will be revealed over the course of the game. Unfortunately, being a spirit-eater is a lot like having a drug addiction. The longer you go without consuming a spirit, the weaker you become, until you eventually die. However, if you eat too many spirits too quickly, it's like being addicted to a drug. You'll need to consume more and more spirits just to get the same level of satisfaction as before. So the trick is to balance spirit consumption carefully. A spirit meter will show your character's current hunger level, and it slowly drains while you play the game (though it pauses during conversations). If you rest in the game, you lose a fair amount of your spirit reserve. So if you rest repeatedly, you'll find yourself in big trouble quickly.
The Rashemen city of Mulsantir will act as the "hub city" in the game, the place where much of the storyline plays out and the majority of the game's quests will be garnered. Mulsantir, like most of the other game locations, also has a dark reflection of itself on the Plane of Shadow that the players will visit. The Plane of Shadow uses a new color desaturation technique (that will be available to modders) to turn everything except the color red to black and white. In these shadowlands, certain truths are revealed so a small, benign temple of a god of healing in the "real world" is instead a huge cathedral to an evil deity. A collapsed pier in an otherwise ordinary swamp is revealed to be whole in the Plane of Shadow and it leads to the home of a group of hags called the Slumbering Coven.
The influence meter that's found in MotB is similar to what we saw in KOTOR II, but a bit more refined, with actual ramifications to consider. In the example that we were given, the party that we were traveling in had two companions that were on entirely opposite ends of the morality spectrum. One was Kaelyn, a half-angel, with a more divine and kind sensibility, while the other was One of Many, an incorporeal demon, who was evil through and through.
As you gain more influence with Kaelyn, it would eventually unlock new talents that you can only get through her that were probably a bit more geared to defense, while One of Many had a handful of dark powers to imbue upon you, should you prove that you're worth his trouble. The only problem is that you can't possibly get a solid reputation with both, as when you gain influence with one, it goes down with the other. Eventually, if you gain too much influence with one, it won't sit well with the other, and they'll eventually leave the party. If you really upset a companion, they may even turn on you and attack, forcing you to battle a formidable opponent.