I’ve been trying to pin down this bit of lore. My understanding is that Uther was sundered in two: half of him is lost to Frostmourne, half ferried to Bastion.
Within Frostmourne, Uther plays a key role in WotLK. He comes to understand that Arthas, his student, is gone, replaced by the master of the Helm. He forgives his former student:
Uther the Lightbringer says: Arthas…
Uther the Lightbringer says: Alas, hero of Azeroth, you give me a greater gift than you know.
Uther the Lightbringer says: Long have I struggled to forgive the prince for his terrible transgressions.
Uther the Lightbringer says: My soul has been wracked with unbearable anxiety, dark thoughts… distancing me from the Light.
Uther the Lightbringer says: I recall clearly the gleam of pride in his eye as he stood before me, eager to defeat the enemies of the Light…
Uther the Lightbringer says: Eager to defend his people, no matter the cost.
Uther the Lightbringer says: It is this memory of Arthas that I choose to keep in my heart.
Uther the Lightbringer says: I shall always be in your debt, friend.
Uther the Lightbringer says: Thank you.
Uther in Bastion goes the exact opposite direction and becomes corrupted by his vengeance lust.
So my question is what happened to Uther’s Frostmourne half? Shouldn’t he have been ferried to SL as soon as Frostmourne was shattered to form a “many threaded rope?” How does this “rope” process work when the threads are fundamentally at odds with each other?