My opinion s that Harry is groomed by almost everyone to take over Mabs mantle. meaning defender of reality and holding the outer gates.
I think somewhere with the mothers or the gatekeeper it was said that Mabs responsibility is defending all of reality „in this age“. Mab took over around Hastings? And was mortal before that.
So she probably was a Starborn, because its pretty nifty when the main focus point of defense against the outsiders can’t be corrupted by them.
So in the next age, it is humanity who will take over the defense, not Winter anymore.

Most factions prepare starborns to be in position to take over the defense mantle, because with this mantle, there also comes lots of additional, collateral power over how our reality looks like. Makes a lot of difference if the ruleset after the accords is written by Drakul or by Harry.

Maybe Harry enlists or press-gangs the inmates of Demonreach to be the defenders or consumes all of them and sets up a new defense line. But this will be his last mantle.