: Well, don't forget someone built the pyramid, and then there were quite a lot
: of centuries during which stuff related to it, such as the Alien Pipes,
: could be spread across the world... And someone from the civilization that
: built the pyramid long ago would have traditions and memories handed down
: through all the generations that they could tell people about, such as
: "dude there are these pipes that have something to do with something,
: but a stupid missionary stole them from us long ago so we don't know where
: they are". And maybe Muller happened to hear something like that, got
: interested and searched the world for the missing artifacts...
: Here's a possible explanation for how he knew about the green oozes and the
: brown potion, and yet didn't expect monsters to be there: perhaps the
: suspicious-looking symbols all over the walls are some kind of writing,
: and Muller knows how to read them. They went into the pyramid, got
: surprise attacked by monsters, and after that he read up on pyramid
: artifacts by studying the walls... I dunno.
We kind of came to the conclusion that the tribe who built the pyramid was the Tlecoatcha. It is possible about the stories passed down from generation to generation considering that the tribe was obviously expelled from the pyramid when a bunch of them became zombies. The idea of the writing on the wall is a good idea, however from what we can tell Muller never reached any levels where their was writing on the wall. But as it was said the Tlecoatcha probably passed down some story like "... and to gain passage to the inner sanctums the green guards must be passed. However, neither the sword nor arrow cannot harm them only the bad smelling brown potion on Happy Happy Carnage Carnage. The one next to the red cloak which you need as well."