Ok, after much experimentation, I've finally found a combo to call my own with Valk. It's:
6C, 2C, 6B, No Command, 2C, 6C, jA, B, jB, 214B, 9D, (transformed, midair) A, (transformed, midair) A, (transformed, midair) A, (transformed, midair) 236B, (transformed, midair) 236B, (transformed, midair) 214A.
I've practiced with it and I know it works, as I've gotten up to the first 236B (but then my fingers are just having some trouble with timing it right; I'll get it with practice eventually). I have a variant that follows up the (transformed, midair) A's with C, D, B, C, 236236D, Rapid, 6C, 2C, 6B, No Command, 2C, 6C, jA, B, jB, C, but I'm not nearly good enough to pull it off yet (the C, D, B is a pain to time properly, which is why I haven't completed Challenge 9 or 10 as Valk yet).
I'm having trouble with the timing on 214B. If I'm correct, this combo should work in CS1 (v1.03) just fine (the timing on the second attack is tricky). Anyone able to help me here?
Edit: Neglected to mention that this only works when they are against a wall.