Being more specific might help.
Are you looking for ways to grapple over FoM, or what?
I'm guessing that you're referring to spell sunder when you mention barbarian.
For my money, the best way to lock down something under the influence of FoM is tripping. They're not impeded, just prone. They can crawl (which provokes), stand (which provokes), or teleport away (which probably won't provoke, depending on the caster and your feats). Of course, if a GM wants to give a broad interpretation to 'attack and move normally' then you may struggle.