Adds Tiefling Race, Kineticist class, and 1/2 companions in a rather unique situation.
The race is powerful, enough to give you pause between standard Human/Aasimar conundrum, mostly due to Motherless subrace of Tiefling, which gets a free bite that helps with Bite/Trip stacking.
Kineticist as a class is absolutely broken, to the point where a lot of encounters become super-easy due to their cheese. I personally avoid playing the class and pretend it does not exist for the sake of my own "artificial and fair difficulty", but hey, maybe you like that kind of thing!
The companions are...well, barebones I suppose. You do notice that it's a DLC: they do not have party-camp banter, their quests are somewhat boring and their presence is non-existent outside of intro and 3 hastily made zones for the DLC's sake. Yes, they do comment on some main quests from time to time, but that's about it. From gameplay perspective they're probably the strongest companions you can have in this game, assuming you know how to use and abuse the Kineticist classes, if you don't, they're kinda meh. You can also romance them I suppose (both even), if you're into that kind of thing, I usually however do not care much about those in games, thus it had very little appeal to me.
Honestly, safe to skip unless you're into romance and munchkism, or buy on sale I suppose.
(I've tried to do my research online regarding the banter, and some sources say that they do indeed have banter, but when I tried to spam rest to see if they had, I never saw anything.)