I couldn’t figure out how to properly express it in English, but in the panel where Li Bing is reading the pamphlet the “What’s that?” is be said by Chen Shi, with the usage of dialect version of “what”.

The superstitions line cracks me up every time. Li Bing. You’re a giant cat. You don’t get to judge.

Smoke and mirrors - lit. “someone’s being mysterious on purpose”.

I’ll also be perfectly honest, the conversation in the beginning doesn’t quite make sense to me? With the way it goes, it would make more sense for Li Bing to be asking something like “Is that the only reason why you’re reporting it?”, but I checked and rechecked and he still clearly says “why did you wait so long?”, so I left it like that.

Immortal here isn’t meant to be taken literally. In the context of Chinese media, while can refer to beings who can’t die or at least have a very long lifespan, might also mean someone god-like, someone who seeks immortality through the cultivation of qi or through alchemy, or even simply a powerful magic user.