Blue Serum Visions doesn't look like much at first glance, but the fact that it replaces itself while allowing you to manipulate the top of your library makes it a powerful card that is good in all stages of the game
For example, the white Mana Noble Heritage and black Mana Criminal background both grant new triggered abilities that fit the colours playstyle along with unlocking white and black Mana cards for their chosen deck, respectively
(I always imagine it like being what youd get if chess had certain edge cases where rooks could fly, bishops could teleport, or for a second, pawns were driving tanks.) Since the game is built around several thousand collectible cards, and almost every card has some additional unique ability to it one way or the other, it creates an endlessly manipulable, constantly surprising experience
Move over Grey Felt Hat Pikachu, theres a new behatted Pikachu in town
With trample, it punches through chump blockers with ease, and giving another creature that same treatment can close out games in a heartbeat