Wait.
Since Sanctuary wasn't destroyed, Northwemko shouldn't have been destroyed...
Shit.
Uhm... I'm thinking of ways to make this an easy fix.

[Hider=Change in Gale and Korbin's Duel Contains Spoilers Here For Review by Rethel]EDIT: Instead of summoning an Artifact Moralltach on the second to last turn, Korbin will Special Summon Artifact Achilles so Gale wouldn't be able to attack. On the next turn, instead of Xyz Summoning two Durendal's, Korbin will Summon a Constellar Pleiades and an Adreus, Keeper of Armageddon. First he'll use Pleiades's effect to return Sanctuary to his hand, then he'll use Adreus's effect to destroy Northwemko. After that, attack for the kill.[/hider]