Doubling the amount of life somebody lost in a turn can be deceptively powerful
Rivers first ability is Meet in Reverse, which lets you draw cards from the bottom of your library instead of the top - which is funny, if nothing else
The Saga mechanic from the upcoming set Dominaria seems like a great mechanic, but creates a new visual layout for the card the text box is over the card type, for example while it makes it more unique it also adds cognitive noise
I think the PlayEDH Discord does a great job of matching power levels and setting good expectations for the nature of a game, but what if youre off to a MagicCon for games with strangers
Dark Confidant, or "Bob," as it's otherwise known, also has the honor of being inspired by a Pro Tour Hall-of-Famer, Bob Maher