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it was found through usage that was taken from an old RoA ladder of Gen3 NU. To be honest, I actually did not know that gen3 NU was found that way. Any way I can find more information on that?
From the explanation I was given, ADV NU was formed from all of the mons that were completely non-viable in ADV UU. ADV UU was formed in a similar way for all the mons in ADV OU that were unviable, which is why they have such a large list of mons and a big ban list. You can probably ask Oglemi for more information about it since he was basically ADVNUTL for the longest time