How Many Game Changers Am I Allowed To Play
2 Sheoldred, Whispering One Another powerful creature with a reanimation ability built into it, Sheoldred, Whispering One takes a little bit of time to get going, but the longer it is in play, the more value it generates
(If a player leaves the game during their turn, that turn continues without an active player.)
I dont know that it is the best of the Charms (I would give that title to Izzet Charm), but unlike Izzet Charm, where you overpay by one mana for any of two to three desirable effects, you more-or-less break even on each of Selesnya Charms charming possibilities
Its the most annoying card in all of Magic (despite its extreme goodness)
We've got a few solid recommendations here to keep you learning the game