Took about 30 tries playing around with different CEs and finally found a decent mix that worked well. Used Mash for Np charge and to block the first Excalibur. Prior to this, I avoided using Mash’s defense buff since it carries over after her death. However, I tried using it this go around and it clearly made a difference in reducing damage from 2 turns of Gawain’s normal attacks. Also had 500-year obsession, which I usually avoid, but figured I would try it since Archuria has no dodges. Anyway, this was my best attempt and could be considered to not be a “true solo”. In the end it comes down to getting very lucky with critting on arts cards for quick Nps, having Archuria’s Np drain trigger and hoping Gawain doesn’t crit back. Was a fun challenge quest and I’m just glad I finally cleared it!