You receive many things: Kings rock, Metal coat, Upgrade, Dragon scale.
You get a star on your trainer card and it'll change it's colour, (It may not sound like much, but it's probably the 2nd/3rd hardest star to get) :)
it is far north on seven island. !!CAUTION!! THE TRAINERS THERE HAVE LVL 100S not easy to beat!
in the celestial tower
you need to beat though trainer
It is on Seven Island, to the north.
You can find him when you go to the battle tower and battle on single, he's the 21st and the 49th trainer you face there (last trainer on the 3rd and 7th bunch of 7 trainers).
Beat the trainer tower.
The Dragon Scale is in the trainer tower at the top of island 7. you must beat the trainer tower on doubles or beat it twice. Also there is one located near in ruin valley on six island need surf to get it.
star for your trainer card. (once you get all five stars, you beat the game.)
it is far north on seven island. !!CAUTION!! THE TRAINERS THERE HAVE LVL 100S not easy to beat!
get Pokemon Lv20-25 with high Att or high Def.
I think you need to beat trainer tower or defeat all the trainers on every island.
Only the trainers in battle tower (the battle tower trainer's Pokemon will not be recorded in the pokedex)
after you beat them your free to do whatever like catch legendary Pokemon and get your trainer card to change color by getting stars, and you can go to the battle tower!
When you reach the top of trainer tower the owner will be there if you speak to him he gives you a special prize along with the fact he posts your time record downstairs. The prizes are as follows: King's rock, Dragon Scale, Up-Grade, Metal Coat.
a trainer has one in battle tower
battle tower
You can get a 5 star trainer card, beat 9999 people in the battle tower (in a winning streak), get into the ribbon syndicate, make Pokemon go to lvl 100, and battle people at wfc in battle tower! Good luck! PS: if you want tips i have a 4 star trainer card so im a pro and i did not use cheats at all!