Quote Originally Posted by schm0 View Post
Shadow blade creates an object made of solidified gloom. It does not bestow a magical effect on the creature. The creature is precisely the same as it was before it cast the spell.

For the purposes of casting the dispel magic, this should be obvious to the caster and they would know to cast it on the object.
It does bestow an effect on the caster, they can reform the SB in their hand.

I think any of the 3 possible targettings would dispel SB.