Consider Fergus McDuck as a swap for Prince Phillip Royal Explorer in Emerald/Steel, or use him in aggro decks as a way to protect key characters
The only upside is the ability to cheat on the mana for an equip cost, which is already a pretty situational benefit
The Angel then gains, You cant lose the game, and your opponents cant win the game. Now, you cant do this at instant speed, but its still a very potent effect, and being able to put this on whichever Angel you choose makes it an essential card for any Angel deck
When Surge of Salvation resolves, you and permanents you control gain hexproof for the turn
Immediately, this makes Zariel a good choice for aggro decks and tempo decks that can curve into it
Pair with the Misty supporter card for super-quick knockouts