Evolve a gastly that you can catch in the sprout tower
Chat with our AI personalities
Trade Haunter and you will get a Gengar.
Via trade.
you can't find haunter in Black
Haunter evolves by trade
You can't catch a Haunter in Emerald. You can trade for one, you can find a Duskull/Dusclops at MT Pyre, but you can't straight out find a wild Haunter.