The entire series has been building around Outsiders being the enemy, and now you got Mother Winter, Odin, and Rashid as Outsider gods... Anyone else you peg as an Outsider?
Look again at Mab and what her Fortess actually is, It's a giant's home, a Jotun? MW is certainly an ice giantess... The whole story is predicated on the idea Outsiders finding a place inside. The Jotun Odin fought in his era became the source of power for the winter court, ergo denying them the ability to mirror those things in the darkness. That's the whole point of the fairy courts balance.
Hell the whole point of the DF is giving them masks in reality that are copacetic with existence.
Look at the stars on Lady Nights neck in CH, vs the 5 points of creation, the five times of DR, each syncing to a different source of creation or the five current in the Fae pantheon, Mab, Titania, EK, Kringle, and.... Nemesis.(more akin to Ursula here, the Queen version)
and go back, way back to the beginning, to when any of these things die. They all enter the same individual shadows, the same... imprint on the universe. Those five imprints are those 3 who walk before, he who walks behind and Nemesis.(the Mother version) It's why they are described similar to necromantic creatures being 'deep', they are echo's on creation that don't really wanna let it go.
They get to be so, because they tend to die per their descriptive name, others probably don't have the same description even if they come from the same archetype. Those who walk before the end, and he who walks after, Death. (hhwbh as death has many connections...) and the Judge who decides the Fate. The Horsemen once they have a viable host to be their beast of burden.... anytime those specific consciousness(or whatever, collective spiritual identity) manifest it's in tune with that description causing, by their own nature, The End. (hence why Nic specifically was calling apocalyptic powers of Disease, a previous horsemen he does not want an identity/aspects to come back to, so he spreads it out and then takes the smut with Anduriel.