Trade Haunter and you will get a Gengar.
Via trade.
you can't find haunter in Black
Haunter evolves by trade
Have someone trade you a Haunter edit: i found one in cliff cave so i dont know but yeah link trade a haunter.get somebody to trade you haunter or gengar
Trade Haunter and you will get a Gengar.
Via trade.
Kadabra, machoke, haunter 'Just trading' - Kadabra; Machoke; Graveler; Haunter.
forest at night
You trade it at a high enough level
Gengar is a ghost-poison type pokemon that evolves from Haunter.
Ghastly evolves into Haunter at level 25. Then Haunter evolves by trading.
you can't find haunter in Black
Route 8 Safari Zone (Nighttime)
look in the Pokemon tower in lavender for haunter. note, haunter is hard to find in the Pokemon tower
Haunter evolves by trade
Haunter can be found on Route 8 or in the Safari Zone.