In our last game one of the players encountered the Himalaya research encounter card. It states that a monster is spawned (so it isn't an ambush) that should be encountered. The monster that was drawn was a mummy which immediately moves to the pyramids when it spawns. So what should happen in this case? Should you not encounter the monster because it moved to the pyramids? Should you treat the spawn as an ambush instead? Should you first encounter the mummy and then have it move to the pyramids? Or should you just keep the mummy in the Himalayas?

Is there anything in the errata mentioned about this?

This question has come up before (a google search will turn up many hits). One time someone actually sent the question into FFG and got an an answer (full thread: https://boardgamegeek.com/thread/1253228/complex-encounters-and-spawning-monsters ). The relevant part is the (currently) last post in the thread:

I received an answer from Nikki Valens for this situation. The official ruling pretty much agrees with the last couple of posters.

- Spawn the monster (Elder Thing)
- Move the monster to Antarctica per spawn effect
- Encounter/fight the monster per card effect
- Resolve the pass/fail effect on the card depending on whether you defeated the monster

And yes, it is possible for the Elder Thing to then remain in Antarctica after your encounter is over.

In this case discussed in that thread the monster with the spawn effect is an Elder Thing, but the same logic applies for your case

(Edit for style)

My google-fu must have failed me, I couldn't find anything

That answer clears everything up. Thanks!