MLP-MTG: turn to stone

This card is strictly better than Arrest. Not only does it have a lower mana cost, but the shroud also prevents it from being bounced.
Furthermore, it's in the wrong slice of the color pie. While the flavor may fit Black and/or Green, the effect is White's specialty. If you don't respect the color pie, the colors lose their meaning; it's less of an issue in an isolated set, as long as you're consistent (keeping distinct strengths and weaknesses for each color), but a lot of players will hate you for "dissing the pie".