Apologies if this has been asked before, couldn't find anything related to this question

If I have a game on GOG (Warhammer 40K Gladius for example) and I want to purchase the DLC, do I have to buy the DLC from GOG?

If I can find it cheaper elsewhere will it still work with the GOG version of the game? In particular, a lot of places sell Steam keys, I'm guessing these won't work?

Thanks in advance for any help given

You have to buy the DLC on GOG as well. Steam keys won't work as it's a different store.

Most likely they won't work, at least not straight as they are. You may be able to tweak those to be compatible in some cases, but you can forget any automatic configurations and such if there are any.

You should also consider this: you can't buy only a DLC from Steam, so you need to buy the game too, and that probably won't be cheaper in the long run.

If you find some cheap keys some place, you should also remember that they may come from questionable sources, and can be deactivated by Steam without any warning.

It could be an interesting thing to play with and find out how it goes, but you won't be saving any time or money by trying to mix and match things from different stores.

OK thanks both, that's pretty much as I figured. Bit annoying as I'm now tied to GOG's prices or waiting for a sale on DLC if I don't want to pay full price

Yeah, I don't tend to buy from questionable sources if I can avoid them, however, there are some legit places but they only sell Steam keys sadly. They do still tend to be cheaper than Steam though, which is something. Shame!

Anyway, thanks again, appreciate the quick responses

a bit of trivia but CA is actually exploring to see if they could make this work in the future.

Total War games already use their own personal launcher, about in the same way Slitherine does only here you can see all your total war games available and with their exclusivity deal with epic to launch their latest SAGA game Troy there is talk of how customers in the near future could be able to buy dlc from steam and see it added to their epic version since all games register on their own launcher

Could be cool

Slitherine btw does already provide that what you buy on their personal store will grant you steam keys too, maybe they will out to gog too at a certain point or make more available themselves though their aim is much smaller i belief then CA in that regard

and there is at least once a year a skulls for the skull throne warhammer sale going on appliable to every platform and the games themselves included with dlc go at least twice a year too on GoG