So... if a creature has 5 HP or more, it's not affected, while if it has less it is partially blocked. Sort of like a weaker reversed Gravity Shield.
I actually really like this idea and hope it (or something like it) makes it to the game. The upped seems a bit too much like Skull Shield - I'd opt for just making it cheaper with upgrade - but I can definitely see this being used, especially in conjunction with mass CC.