Haunter can only be evolved into Gengar via Trading (such is the case in all Pokemon titles that include Haunter, not just Silver).
You have to trade it to an other game for it to evovle.
trade it then it will evolve
Haunter evolves into gengar once you trade him.
yes into a haunter and the trade it to evolve into a gengar
When you trade him/her like in all other generations.
No, you don't need the National Dex to evolve Haunter in Pokemon SoulSilver. You just need to trade it with a friend then trade it back. Then, you have a Gengar!
You have to trade the Pokemon to evolve it.
You will need to level up Haunter to level 50 to evolve it in Pokemon Resolute.
Trade Haunter with any Pokemon to make it evolve!
Actually, Haunter does evolve. Its evolves into Gengar when you trade it.
In order to evolve Haunter, u have to trade and it will evolve into a Gengar.
Yes. The pokemon is Haunter. In order to evolve Haunter you will have to trade him with a friend and he will evolve. Just trade back to get Gengar.