inflicting advantages with negative limitations

[McAllister]

Originally Posted by Ghostdancer

Why aren't you just using Shadow Form (3-D Movement, +20%; Can Speak, +5%; Illusionary Form, +25%) [-12]?

This looks like it might actually be what I'm looking for! What's Illusionary Form from, and what does it do? Does it take 3-D Movement and add looking 3-D?

Also, is there some reason Shadow Form should take away someone's ability to speak?