upgrading a mythic

[Protey]

So I completed the quest Duties, Tasks, and Deeds and am about to embark on Forging a New Myth when I realized I never unlocked the WS. Now I know I can retrieve the weapon from Abquhbah by turning in another weapon to upgrade, however I get this warning:

"Abandoning an item will cause Paparoon to purge your records, resetting the process. As this is irreversible once executed, please use your best discretion."

Now I already received the Laevateinn and just need to go do the fight. So I am wondering if anyone knows if I have to go back into nyzul and get another base weapon to unlock the WS or can I just get it back from Abquhbah without losing the ability to complete the quest.

[Martel]

The WS will be automatically unlocked during the mythic BC(right after balrahn uses the mythic WS, iirc.) Then after the BC, you'll have access to the WS anytime you're wearing the mythic.

So really, you don't need to unlock it at all.

[Terravcota]

You don't need to unlock the WS prior to the fight. You will get access to your WS during the fight with Balrahn after some dialogue. I've never unlocked Mordant Rime.

[frodnonnag]

or you could go do floor 100 nyzul with a friend or two, get a 100% drop of the weapon and unlock it in an evening.

[Protey]

worked just as you said Martel and Terravcota, thanks!