When Vigor is put into a graveyard from anywhere, shuffle it into its owners library
Same cost to play, cheaper to activate, same discard-to-tutor effect, but it lives on a 2/2 body that requires summoning sickness to wear off and can be removed before you get value
No longer does the deck have to split slots between ways to win and ways to take extra turns
The official Pokmon TCG account uses the term, Reddit has entire threads dedicated to them, and any collector who has spent time browsing binder pages knows exactly what feeling you get when you land on one
Releasing newer cards that are more powerful makes older cards less effective, forcing players to buy the new sets in order to keep up -- but this isn't the only factor at play
No, none of the sliver commanders or non-legendary slivers are banned in Commander