Basically, you have to preserve LB3 through the entirety of the Dragonsong War Phase, including the Eyes after you beat Nidhogg, then use a Tank LB3 to make it so you can heal Haurchefant to full in order for him to survive the cast from Charibert.
Then you have to kill the spear before it finishes casting Pierce. If you don't? Then back to Thordan you go.
And then... https://twitter.com/RadianceXIV/status/1519813083039903750
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Congrats to azuarc for winning GOTD2 http://i.imgur.com/v58wdlU.png