All the way until you know how to keep your MTG cards in mint condition
Well, after the Lin Sivvi debacle, Wizards changed the legend rule and made it so that if two copies of a legend were on the battlefield at the same time, they would both immediately go to the graveyard
I know some parts might be contradictory (Feline Ferocity is the most valuable despite all my criticism), so let me know in the comments if you think I missed anything
I like Thopter Engineer better than the other three-cost options because of how often haste will function like an enters-the-battlefield trigger here
All of your creatures have very low stat lines, making it hard for them to be threatening
When this creature leaves the battlefield, the exiled card's owner creates an X/X blue Illusion creature token, where X is the mana value of the exiled card