What level should you use the dusk stone for misdreavus in soul silver?

You should use a Dusk Stone on Misdreavus at level 30 in Soul Silver to evolve it into Mismagius.

Here's why:

* Evolution Level: Misdreavus evolves into Mismagius at level 30 when holding a Dusk Stone.

* Catching Misdreavus: You can usually encounter Misdreavus in the following locations:

* Route 34: After obtaining the HM Strength

* Route 45: After defeating the fourth Gym Leader, Morty

* Eterna Forest: After defeating the fourth Gym Leader, Morty

* Turnback Cave: After defeating the seventh Gym Leader, Volkner

Therefore, it's best to catch Misdreavus around level 25-28 to ensure it's already close to the evolution level before you use the Dusk Stone.