Abyss: Floor 85 (D. Corvus): BEATEN!
■ Team Comp:
• Arkasus (guardian)
• Angelica  (6* Awakened; S3 +3; 33,367CP; 1006 DEF; 14,435 HP; 141 SPD; 24.0% ER; 5.4% MI; Celestine @15)
• Falconer Kluri  (5* Awakened; S1 +5, S2 +6, S3 +3; 33,288 CP; 1124 DEF; 13086 HP; 170 SPD; 25% EFF, 7.0% ER; +18 MI; Aurius @15)
• Silk  (6* Awakened; S1 +5, S3 +3; 35,117 CP; 181 SPD; 166-, 26.0%, 161.0%, 32.0% EFF, 12.0% ER; 5.8% MI; Daydream Joker @30)
• Cidd  (6* Awakened; S1 +5, S2 +5, S3 +5; 73,843 CP; 146 SPD; 3349, 90.0%, 253.0%, 28.0% EFF, 5.0% ER; +3 MI; Elyha's Knife @30)
For the first wave, the goal was to come out with everyone's skill ready and max soul charges.
The mini-boss and its minions were your run-of-the-mill enemies, just killed the mini-boss last and with S1 skills near the end to achieve my goal.
□ SECOND WAVE IMPORTANT DETAILS:
The boss' attack/damage is drastically increased after he takes 20 turns.
I avoided soul-burning Angelica's S3 whenever I could in order to use Arky as much as possible.
▪︎For the second wave, unfortunately, there is no real strategy to recommend due to the battle's RNG fight mechanics (the boss randomly chooses who'll he attack with skill 'Devil's Descent').
The only thing you can do is make sure to give your heroes a cushion above 10k HP, and if you can't then hope he doesn't hit team-members with sub-10k HP.
I first killed the minion "Yellow Crystal" which prevented the boss from receiving decreases in combat readiness then focused the boss for the rest of the fight, all the while keeping hero "Silk" S3 on cool-down to suppress the enemies' speed and using Arky to burst the minion "Yellow Crystal".
I didn't start recording until it seemed like I might actually win (and is why the video is so short).
Arkasus only requires three soul-charges, so he allows for spammable damage. Although "Dark Corvus" is immune to damage "modified by target max health", the crystals are not, so being able to nuke the crystals more often was good.
Angelica (besides healing) gave buffs 'immunity' & 'barrier'. 'Immunity' kept my team from having their combat readiness reduced when "Dark Corvus" used his AOE attack ('Macerate'?) and 'barrier' helped my team survive his attacks (especially 'Devil's Descent' when able).
Falconer Kluri's job was to soak up damage from "Dark Corvus" 'Devil's Descent' by wearing artifact 'Arius' and to aid in debuffing 'decreased defense'. She also has a rune in her specialty-change skill tree that provides 2% health recovery to allies whenever she takes a turn, so she also aided in healing my team (especially since she's so fast).
Silk was the crowd-control, speeding up my team and slowing down the enemies. I gave her artifact "Daydream Joker" to aid in killing minion "Yellow Crystal", and once it was dead, she pushed back "Dark Corvus" allowing my team to get in as many hits as possible before he took a turn.
Cidd, once again, was my all-star. He helped to keep up debuff 'decreased defense', and because he self-buffs 'increased speed' he was able to out pace the enemies frequently which allowed him to take advantage of the debuffed enemies. I recently acquired artifact 'Elyha's Knife' (and was able to max it out thanks to the refresh of the "Powder of Knowledge" lobby shop) which gave him a static 20% penetrate/ignore defense that allowed his attacks to do more damage. Thank God he didn't get hit with the bosses S3 cause he had less than 10k HP >.<
Hope this helps!
P.S.: It wasn't until I watched the video that I realized I had mis-matched rings on "F. Kluri" and gear swapped on other heroes :-P I guess it worked out cause it gave them more health so they didn't get one-shot from the boss' S3 (there were a number of near-pop occasions)!