I own the base game on Battle.net.
If I buy the expansion on steam will I be able to play through Steam? I just want to play on my Steam Deck and I hate using the workaround. I also refuse to buy something I already bought the ultimate edition of, on release.
you will need the base game on steam as well.
Thank you for the response. That is unfortunate, I guess I’ll wait for a Steam sale or see if PoE 2 will be on Steam 
Forcing people to purchase twice is aggravating.
The expansion includes the base game - at least on the pre-release store page.
Unfortunately, from what I can tell, this only applies to the “bundle” which is $90 CAD and is the equivalent of the standard Edition expansion which would be $54 CAD on its own. So they are charging $36 for the base game to be bundled with it.
I want to buy the Ultimate expansion for Steam at $120 but I’m not going to bother if I have to purchase the base game again. I do not support these kind of tactics. I’ve already shelled out $150 for the ultimate edition of D4 Base back in 2023.
Only the bundle version for 70 includes both and its base edition of both.
You can try adding a non steam game to steam ,not sure it will work though .