it helps you run into legendary or rare Pokemon it works better if you have the mystery part, sometimes it doesn't work just carry it with you and don't press use. I have it and one time I ran into a Zapdos. Also I'll give you a tip at the final maze when you reach the snow level sometimes you will run into a suicune. (you sometimes have to go there three times.)
you don't activate the secret slab the purpose of the secret slab is to summon legendaries in certain dungeons
Obtain a mission that allows or has a reward that involves getting a secret slab.
the secret slab lets you find certain legendary Pokemon in cetain floors of a dungeon. for example, with a secret slab you can find darkrai on floor 3 of the miracle sea.
The secret slab enables you to meet legendary Pokemon after you reach the marine resort.
i indeed did get celebi once getting secret slab and it will be a shiny celebi
sometimes on a mission, it will say to explore with the client to find a secret slab, so when you complete the job you get to keep the secret slab or you can just put in wondermail codes to obtain it.
look it up on google ("pokemon explorers of darkness secret slab") and enter it on the main menu
You DO NOT USE the MYSTERY PART OR SECRET SLAB. You keep it in the bag for it to be able to do what it does.
beat dialga to get to mystifying forest. 2 get a secret slab go to apointlessplace.net and you can make your own wondermail.
Yes, you neeb a secret slab or a mystery part to get legendaries in the final maze
Yes just unlock the marine resort then get the secret slab or mystery part then go to amphplanes 7th floor and just look for it
it lets you get certain legendaries