Magma key

I have gone to the well and have tried *using* the magma key but keep getting the response "cannot be used here". I'm stuck. Any suggestions?

I'm assuming that you've had the chat back in Baron in Cecil's room where Kain gives you the key. After that, when you go south to Agart and "talk" to the well and use the key, there should be an earthquake and a hole opens in the mountain outside.

It sounds like you did this (minus being able to use the key) already, but I wanted to check that you didn't miss anything.

Flying Mullet is right. Talking to the well then using the key when the Item Menu pops up should fix your problem.