I continued to collect them simply because, the more I looked around, the more I found, and it simply progressed from there
Because the one-shot effect that returns the card isnt an ability that goes on the stack, it wont cease to exist along with the leaving players spells and abilities on the stack
They dont have zones, but they arent needed at all
There are also a trio of team up Legendary cards which will be appearing exclusively in pre-release kits
Meaning that if you have a way to discard it in the first place, creatures, enchantments, and sorceries with madness can be cast at instant speed
There are plenty of other scenarios where either you dont have other creatures on the battlefield, they cant profitably attack, your Seafloor Oracle gets Lightning Struck before combat damage, and more where you wish your four mana creature in your aggro deck would have done more