Here's the ending if you free Wyll from Mizora's pact, rescue his father from the Iron Throne prison, Wyll becomes the Blade of Avernus, and Karlach becomes an Illithid.
In this ending, Wyll is not trapped in the hells, he just travels there anytime to hunt demons. He's free as a bird after he's released from Mizora's pact.
just realised, Wyll still wears his sending stone eye that was from Mizora. You'd think he'd try to get that replaced or something
So, even without Karlach, Wyll can still end up in hell? Though at least it seems he's able to leave when he wants.
In this ending, Wyll is not trapped in the hells, he just travels there anytime to hunt demons. He's free as a bird after he's released from Mizora's pact.