Bel is the leader in Avernus, but the MM says Zariel. Which is correct?

@Inxanity1 @ChrisPerkinsDnDSo, the current Paladin UA implies Bel is the leader in Avernus, but the MM says Zariel. Which is correct? MM – UA is never canonical as is subject to change #WOTCstaff

— (((Mike Mearls))) (@mikemearls) December 20, 2016