If an effect tells you to flip multiple coins at once and you haven't flipped one or more coins already during that turn, Edgar's last ability modifies that set of flips
It's a one-mana artifact creature with a relevant ability, which is good for any deck that wants to dump lots of artifacts onto the board (Affinity, Urza)
Guardian of Faith: Sonic sometimes needs protection for him and the crew, and the Guardian of Faith will provide just that and a flash body afterwards
The first are the usual Booster Boxes and Illumineers Troves, which include a hearty booty of booster packs for you to rip open
Since that will be happening a lot, there's no reason not to toss it in
With planeswalkers, increasing tempo and a fair amount of paying life for things the premium on good burn just keeps going up