-
There is no key you get from Bergusia forge, not like the other forges, anyway. To get the fourth key, you have to complete all the steps to the Key Mold quest you get from Ada-1. Without the Key Mold quest, you will not get a key from Bergusia Forge.
-
Whoops, sorry. If the butterfly key is the one you're missing, you're good. The butterfly key comes from Izanami Forge. That should come back around in the rotation on Monday, so just do a normal max temper run then, and you should get your last key.