SOLVED. Book that is about an expedition in mexico, has references to mayan/aztec (mainly the temples)

[Hannah]

(i'm working on an assignment and the topic triggered a book anyways - ) the book starts with a historian(?) and his partner arriving in mexico to meet their local guide and they're going into the wilderness to look for a temple or something. the local guide really doesn't like the place and is super superstitious. i don't remember how the middle of the book goes but there were mentions of human sacrifice to this god/deity who appears as a bat and drains the blood from the sacrifice and the drained body turns into a zombified minion(?) anyways this god/deity got sealed away but the historian and his partner accidentally awakened him and their guide gets attacked and turned into a minion. the god tries to take over their bodies so they can move out of this wilderness/place they were sealed in but the partner figures out that the zombified minions can be beaten by fire so they set all of the minions on fire and it looks like they've defeated the god. at the end, the partner finds the historian person and is like wow i thought you were dead, lets go back home and put all this behind us, and doesn't notice that the guy has been zombified. I think there was also a translation on the outside of the temple that needed to be done, and it told the story of who was sealed away in the temple and why people shouldn't approach the temple? I think its been around 10 years since i read this book

okay i posted this and 15 minutes later i find the book via looking up random keywords related to the book

[Rainbowheart]

Glad you found it!

London, 1850 for the link.