I'm in The Creator Ruins (level 1) in chapter 2. I've given the golem signet ring to the seal guardian, and he disappears like he is supposed to do. But the little barrier behind him is still up and it says that it requires a key to open, but I can't find the key anywhere. Does anybody know where it's supposed to be ??

Any help would be great.

First a word of welcome to a fellow dutchy.
Second a word of sorry that I don't recall in detail, but I think I just busted the guardians and took the keys from them. Don't know of another way to open the doors. I completed the game with the golem signet ring still in my possession and without using it.

Possible Spoiler
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It's been awhile since I did that, but either the golem gave you the key or you have to find it in a chest in one of the other rooms to the right of the golem.