I didn't know 2E had much reference to Tharizdun, but then again I wasn't playing DnD for most of the 2E era.
Thinking about it, there are a couple of things I could retcon to work with Tharizdun about the session.
There was a purple/black curtain of light that lead us to the pyramid and we had a vision of a magic staff that could be used to gate in an army of gnolls. I'd say it could have easily been a false vision, which instead would have helped to unlock some portion of the dark one's prison. I'd ask, but it is moot, we'll be continuing with our regularly scheduled session next week.
Thinking about it, there are a couple of things I could retcon to work with Tharizdun about the session.
There was a purple/black curtain of light that lead us to the pyramid and we had a vision of a magic staff that could be used to gate in an army of gnolls. I'd say it could have easily been a false vision, which instead would have helped to unlock some portion of the dark one's prison. I'd ask, but it is moot, we'll be continuing with our regularly scheduled session next week.