As a mage I got to say it was sort of difficult. Here's what I did:
I used Paladin equipment (13% light resist, 65/60/66 MRM, Fully Defensive). Any Light FD armor + weapon + shield could probably do since I didn't use Zorbak ally assist to turn Baorus into undead and gain Paladin bonuses. I had Elahi Irt of Osiris for stats and Light res. I also had Poelala pet equipped but not the guest.
First I stacked celerity using Shadowfeeder Pendant and Purple Rain (Poelala pet unequipped for cheaper SP). I should've cast Moonwalker too but I forgot. PR again to return to original HP/MP values.
After that I converted my HP to fill up my SP bar, and converted the SP to Chi Shield using Dragonlord Shield (only one cast). This way, when his Burn damaged the chi shield, it didn't heal him.
Every turn, I attacked him with the light weapon and I did one cast of Dragonlord Shield to increase my Chi Shield (more efficient when done only once per turn). When I ran out of SP, I just converted my HP to fill up my SP bar again. When I ran out of HP, I used Cherub Protection to heal up (any INT-based healing spell could probably do). I did this until I ran out of MP.
I just continued to attack him with the light weapon, hoping that his HP would go down before my Chi shield did. In the final few stages of the battle my HP, MP and SP bars were all depleted and I only had the Chi Shield to protect me.
I was only able to do this one time, so it may not work all the time especially if you get stun-locked or if the Burn level gets too high. Do note that I was also able to beat him as a Vampire so there's no need to remove your subrace
EDIT: I was able to do it again with 20 HP/20 MP left but with around 3k Chi Shield remaining
< Message edited by Veleqwii_Fox -- 4/8/2021 11:55:03 >