Don & Leo, Problem Solvers takes the techy Donatello and the analytical Leonardo and turns their virtues into a creature with a built-in blink trigger for one of your artifacts and one of your creatures
First, What Even Is a Format
Another advantage this card has is that you can actually create copies that keep bringing spells back without having to sacrifice any of them to the legend rule since its not a legendary
Stack or Replace: Some Special Conditions stack with each other, but any time you inflict a the same Special Condition on a Pokmon, like Poisoning something which has already been Poisoned, the newer of the two replaces the older
In my experience, one of the main things that stands in the way of slivers is the pesky creatures around to block
1999 Pokemon Base Set Shadowless Holo Mewtwo PSA 10 Recently Sold for $4,900 [Source] Check current eBay listings here