Magic Resistance on a single enemy is hardly a threat, but on all three enemies made for a nightmare. I initially tried to do level 20 Asterios, but after a day's worth of time down the drain due to MR I settled for level 60 Asterios (shorter fight and an extra skill for savescum).
Then as soon as I switched to level 60, my luck made a turnaround and I got the run done within a lightning fast four hours. (Four hours is fast when you are doing a RNG-reliant stall solo.)
What can I say? The world is not ready to see a level 20 Bronze solo a challenge quest.
Miyu goes first because she spams skills and her NP has no hits. Both Illya and Chloe have lopsided hitcounts, leaving them both together provides greatest defensive NP gain. Furthermore, Illya only acts twice when left alone.
Fate/Grand Order Revival: Magical Girl Cruise - PRISMA CODES - Re-install
[High Difficulty] Prisma✰Live! Asterios Solo