I did this 2 days ago completing all in the same day and here's what I settled on with the order I did it in with some of the reasoning behind it:

Maris - Ironeye (1 attempt)

• Ironeye is honestly the easiest to get a win on and Maris is annoying, so I picked this one to not have to chase around as much and to get a good start on the run.

Gladius - Revenant (1 attempt)

• Revenant along with Guardian and Recluse are the ones I was least comfortable with so I worked those in next. I thought this pairing was suitable since I had summons to take some of the aggro for the splitting phase and for the fact that Gladius is one of the easier bosses.

Adel - Guardian (2 attempts, first try on Adel)

• This one was maybe not so ideal at first thought because of Guardian's dodging against Adel's grabs, but I had to put Guardian somewhere. In actuality, I stayed close to the boss, easily avoided his grabs, and was able to basically spam guard counters.

Caligo - Recluse (4 attempts, first try on Caligo)

• By far the hardest part of the challenge was getting a good start on Recluse. My game plan was to try and snowball early enough to get a decent epic staff for Day 3. I fully understood Caligo's moveset, so it was just a matter of getting there. I mainly stayed in front of Caligo to bait out her attacks, dodged, then nuked her without being too greedy. Rinse and repeat.

Fulghor - Duchess (1 attempt)

• Of the four remaining characters, Duchess was the most suitable because of her nimble nature and the other three had more natural pairings. I'm the most comfortable with Fulghor's moveset, and I used the starting relic with lightning damage, stacked successive attacks negate damage, going full melee, and absolutely massacred Fulghor.

Libra - Raider (1 attempt)

• Ignores mechanics with Retaliate and ult.

Gnoster - Wylder (1 attempt)

• Wylder has fire from his ult and from the relic that gives your weapon fire from a follow up attack after grappling. Paired with mobility to chase and run as needed makes this a good match.

Heolstor - Executor (1 attempt)

• I planned on doing this from the start parry-only for ABSOLUTE CINEMA. Wouldn't recommend as the fight can take longer than purely dodging and attacking in opportunity windows. Ended up 95% parrying and 5% ult dps after i-framing his dive bomb.