On the locked doors on floors 10 and 15.
You can find them lying around in Solar Cave.
In solar cave (with key) or wyvern hill (with key)
you usually can find keys in the solar cave
To get key(s) go to solar cave and you got to search for it because they r a little hard to find. YOU NEED TO GET THE DUNGEON STORMY SEA IN ORDER TO GET TO SOLAR CAVE.
Either use a key in solar cave or when lombre speaks of stormy sea, speak to whishcash
In any floor i found it on floor 2
In the solar cave behind a locked door that you have to unlock with a key
You can get keys after you beat the game. They are mostly found in Solar Cave, or bought from the Kecleon Market.
In Aegis Cave
Solar Cave. You might need a key to open the box. You can find a link cable inside.
no, you need to go to the solar cave. there is a bit of water around the HM, so all you need is a Pokemon that can walk on/over water
Keys can be found on the floor in Solar Cave and Western Cave. They are more frequently found in Solar Cave, though.