You can get haunter three ways, The first one would be trading someone in Pokemon diamond not a real person and you must give him another Pokemon for haunter I don't know what though. The second way would be going in route 214 in spring path and going into the cave where giratina is they are very common in there. And the third way is to trade with a friend. one more, evolve your gastly which can be found in the same cave. hope it helped!
level 26
You need to trade it with someone. (GTS does not count)
Haunter Evolves by Trade.
i found mine in the old cheatu lv 15 through 19
Gastly > lvl 25 > Haunter > trade evolution > Gengar
Pokemon diamond
Pokemon diamond Pokemon diamond Pokemon diamond
you cant be a Pokemon in Pokemon diamond
you evolve haunter in a trade
She is not in Pokemon diamond.
There is no Pokemon temple! There is such thing as Pokemon diamond.
W.W hanter