I made the following riddle in a RPG.
Albus, Baku and Croco experimented with some ingots. One was using copper, one silver and the other gold.
But none of the experiments worked with the ingots they had. Though another could.
After some changes, Baku ended up richer than before. (gold is more expensive than silver, which is more expensive than copper, just in case)
Croco tried to help Baku with his experiment.
There was no mutual exchange of ingots.
Albus is deadly allergic to silver.
Players could take what Albus had after everything happened, if they guessed what it could be, according to the riddle.
How rich they became?
EDIT to clarify:
The nature of the experiments is not important at all (you can think of Albus, Baku and Croco as alchemists). The important thing here is who had which ingots at the begining and who had them at the end.
It's about logic, as the already given answers point. Even though, you shouldn't make more assumptions than those said.
EDIT to make clear the assumptions of the riddle:
Albus had an ingot. Baku had an ingot. Croco had an ingot. One of the ingots was gold, another silver, another copper.
Some ingots changed their owner, with no mutual exchange. (if A gave his ingot to B, B did not gave his ingot to A)
Baku recieved an ingot that make him richer
Croco gave his ingot to Baku
Albus never touched silver.
You have to guess what can Albus have after everything that's consistent with previous statements and is the maximum possible