In pastrana city there is a guy who teaches Pokemon moves back that your Pokemon forgot.
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move tutor house one heart scale - one move taught
If you mine underground long enough, you will find them, but they are very small, so you have to look everywhere, you can also find them on wild Luvdisc
Select the heart scale in the treasures pocket, then select the put in bag option
Yes, there is heart scale Pokemon modifier and master ball mod
it is used in Pastoria city to teach certain Pokemon special moves
get an action replay and find a cheat for it (i forget what it is called) but there are 2 types, heart scale and master ball. i prefer the heart scale cheat.
You can use heart scales at the Move Re-learner in Pastoria City. He reteaches your Pokémon a move for every heart scale used.
To find heart scales on Pokemon diamond/pearl you need the explorer kit to go underground. once you are underground look for cracks inthe wall, and eventully you will find a heart scale in the cracks.
go underground and mine until you find one
go to a house in pastoria and this guy if you give him a Heart Scale he will teach one of your Pokémon a move. actually he trades shards 4 moves
you get them under ground wich you need the exploror kit and keep on digging and then walla you got it P.S. the heart scale takes time don't forget
you have to get a heart scale and go to the move tourtor andmake it learn it