Neat. I like this a lot. Force of Many strikes me as potentially overpowered, but I am not familiar with Fiendish Shadows (I don't have access to the 3e Fiendish Codex), so it probably isn't. Not much more to say than that, really.
Fiendish shadows aren't in any books but the Monster Manual. They're just shadows with the fiendish template.
My Deviantart, Please enjoy it. Invincible Maiden Avatar by GryffonDurime.