For your database pluton:
Humbaba: Shelter of Athena (Valor shield)
Nabu: Hellfire (Elem shield)
Kingu: Stone of Chaos (Spirit shield)
Enki: Honor of Athena (Valor hit)
Enlil: Erato's Affection (Spirit hit)
Legion: Erato's Affection
Those are purple arms and progression is weird. Not linear or even consistent among the different arms.
For spirit hit i know 21-30 is 150, 31-40 is 200, and 41-50 is supposedly 250. But there is such a higher degree of variability from one person to another based on number of fails, that the base numbers at each level are somewhat irrelevant.
For example, i've seen grade 41 spirit hit arms at 7600 and at 8300... That's the reason I have repeatedly advised that failing on red arms isn't necessarily a bad thing. Because for high grade purple arms it's not the grade that actually matters, it's the overall spirit hit. By being unlucky you actually raise the ceiling for your equipment and strength.
I see a few of the purple armaments missing from the list. Curious to know if that's all from Hanging Garden or is the list incomplete. The upgrades on them don't make sense, I guess I will have to wait for the guide to be updated.