Here is a piece of a dialogue from a video game. A group of mages is going to explore some ancient ruins; they seem to be doing this out of interest.
Elvali: "I can't believe we're doing this."
Savos: "Can you imagine the looks on their faces when we come back?"
Hafnar: "You keep talking like you're sure we'll find something useful in here."
Girduin: "Given the history of this place, it's more than likely there's still some amount of power here."
Savos: "Enchanted weapons, tomes of ancient knowledge, Shalidor's secrets themselves — who knows what we could find!"
I am not sure I understand what the difference would be between could and might if the latter were used in that sentence. When I was reading it the first time, I expected might to be there, as it would be showing their chance of finding anything in those ruins.
Here is what I found on ELU:
The difference between I could go the cinema and I might/may go to the cinema is that the former is associated with reasoning about conditions or alternatives, whereas the latter is just a statement of possibility.
Source: What is the difference between 'can', 'could', 'may' and 'might'? -- English Language & Usage Stack Exchange
Now, does could in my sentence imply some kind of condition? For example:
Who knows what we would be able to obtain, or whether we would be interested in whatever we find here.
Whereas might would imply:
Who knows if there is anything in these ruins. There might or might not be anything in them.
I also looked up the difference in Swan's Practical English Usage (Unit 435). Here is an excerpt:
'general' possibility: can/could, not may/might
We normally use can and could to say that things are possible in general: people are able to do them, the situation makes them possible, or there is nothing to stop them (see 122). May and might are not used in this way.
chances: may/might/could, not can
To talk about the chance (possibility) that something will happen, or is happening, we use may, might or could, but not can.
According to the chances section, it seems might and could can mean the same thing.
Are my suggestions above right, and is there a difference between might and could in my case?