Blacksmith
Brogg takes the copper and crystal keys. You note that both of these keys are identical in size and shape to each other and to the tarnished key you found earlier.
The blacksmith construct is immobile and does not seem to respond to your presence or your investigation. You open the panel revealing what looks like a spigot connected to nothing, just hanging out into an open receptacle, about a foot broad, two feet high, and eight inches deep. Two tubes also hang into the empty receptacle. As you get close to it, traces of something sparkle on the blacksmith's hammer.