For Challenge # 151. If cards like Chaos Orb are legal, I have to assume that Wizards finally got around to regulating how permanents are spaced on the table. It probably involves a playmat with spaces for your first creature, second creature, etc., etc., as well as rules about piling up your land.

I also presume that if cards aren't allowed to cover other cards, that Wizards will eventually print a mechanic that breaks their own rule, because that's what Magic does. Hence Shelter.