it's only in explorers of sky.not darkness.
i think 7 mabye 9.
The Secret Slab takes effect after Manaphy is recruited and the Marine Resort opens up. It causes legendaries to appear in preset locations.
look it up on google ("pokemon explorers of darkness secret slab") and enter it on the main menu
it shows up on the bulliten board every now and then or you can use the wondermail generator on the mystery dungeon website the stoneplate unlocks legendaries in various dungeonshope this helps
you have to do some sort of mission
You can't, try Mewtwo (since he's the exclusive for this version) Dark Crater Deepest Part, B5F, with Secret Stoneplate. He's lvl 47, so he shouldn't be that much of a hassle.
You get to work on the 7 treasures. The 7 treasures is basically you fight legendary Pokemon such as Groudon(the real one), Mew, ect. Then you obtain treasure that is very useful.
You get it by doing lots of missions. Then, you get it from a Elekid.
he is in amp pains if you have a secret slab and a mystery part
Go on the internet and get wonder mail.
concealed ruins with secret slab or mystery part
you can find him in midnight forest fl. 24 if you have mystery part OR secret slab