I don't think it should be gravity.
Main reason being, that Gravity has Gravity Shield for blocking attacks (that come from creatures with more than 5 Hitpoints).
I forget who, but I think if you call this skill Pacifism and make it a spell - it will be a lot better.
Although, I do like the concept of being able to defend your creatures against a shield effect... Gravity already has Momentum to do this, and the creatures get an attack bonus...
um... are you kidding?? you say that it shouldn't be gravity because gravity has a shield that blocks creatures with over 5hp, and you say that instead it should be a light card, when light has hope. In a light hope deck, this would just remove the threat from any creatures with a high enough attack to get past hope, which isn't many when you get the deck going. In a gravity deck you could... reduce the attack of creatures with under 5hp... there are a lot more of those around. This card is good for countering antimatter, good for removing the threat of enemy attackers and it would be cool in combination with flooding. It seems fine in gravity in my opinion.