Your graveyard becomes a toolbox of clerics for you to choose from, and with the other powerful options mentioned in this article it should hopefully be obvious why that is to be feared
The earliest that you can activate Sundial of the Infinite's ability is during your upkeep step, after abilities that trigger "at the beginning of your upkeep" have been put onto the stack but before they resolve
That said, getting value whenever it attacks is strong, so you can draw more cards or kill a good threat
Double-faced cards are a regular sight these days, and as the name would suggest, each one features two Magic card faces: a front face (with an up arrow icon in the upper-left corner) and a back face (with down arrow icon in the upper-right corner)
Raff Capashen, Ship's Mage
The more life gained, the merrier, so youre looking for an Orzhov deck centered around lifegain, self-mill, and reanimate