in the lv 26
Level 26
Gastly evolves at level 25.
Gastly evolves into Haunter at Lv25.
In Pokémon SoulSilver, Gastly will evolve once it hits Level 25.
You don't need to get a gastly to evolve because you can catch haunters in Pokemon tower
Level 37.
Level 30.
level 28
Level 30.
Level 18.
Level 25
at level 40 it should evolve into drapion