Caradhras and the High Pass are redone, Strider has a new quest, the Animus spells now raise Oathbreakers, and a new Recall Companions feat brings back stuck companions.
The undead summons for the epic spells Animus Blast and Animus Blizzard changed from vanilla NWN skeletons/wights to "Oathbreaker" summons, basically toned-down versions of Mummy Dust:
Each spell summons 1 per kill, up to a max of 5 per spell
Summons despawn on rest and death
All classes that can summon familiars, animal companions, summons, etc. now have a new (free) Recall Companions feat that teleports all of your companions to your location outside of combat. Useful when companions get stuck or left behind on certain transitions. Access it via the class radial menu.
Temporarily re-allowing 2 One Rings to be equipped at the same time. This will be disabled again in a future update, when the rings of power (including The One Ring) are rebalanced.