First, with the design part... Any explanation on Holtzman? <_<
Also, I'd like some wording changes. The only effect I can think of when I hear the word 'slowed' is stuck in a time bubble (by attacking
shield). Maybe it should be something like "Only creatures who would normally not be able to attack can attack". This would then also include creatures facing a gravity-pulled creatures, etc.
Now... this card is virtually the second Phase Shield and I'm not sure if there would be people who're willing to accept it. It IS an interesting idea, I admit, since, for example, the opponents would use CCs on their creatures to bypass the shield.
However, I thought more deeply and realized this could fill up the lack of a good shield in Gravity element. I wonder what others would think about it, though.