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Song: Freedom - NAGI☆
Item level:732

%avoidance helps quite a lot for the Light Spectrum phase. Use it if you can without sacrificing DPS.

I had to do this fight as Sub for high damage output however, as Combat I had many attempts at 15-20% but coming out of a Light Spectrum phase was too much damage. Doing it as Sub took a little luck with a second Soul Capacitor Proc, but that was it.

This boss is primarily difficult because of his high damage in addition to his Hard Stare ability.

Hard Stare applies a debuff to the target that reduces healing taken by 10% per stack and will additionally stack a Damage Over Time effect that will continuously stack unless healed to full health.

Because of this effect it is important that we end this fight quickly. In addition to the hard ticking DoT and reduced healing effects the Light Spectrum phase does even more damage.

Each Light (Red,Yellow,Blue) will deal 20,000 damage every 2 seconds.

Because of the high damage from each light it is important that the fight finishes before, or slightly after this phase as Durumu's Hard stare ability will be approaching 5 (50% healing reduction) stacks once the Light Phase begins.

The key to winning this fight as Combat is keeping the Arterial Cut debuff off (Becomes increasingly difficult to achieve) as well as very quickly finishing a light spectrum phase and then lasting long enough to kill him as Hard Stare's Healing reduction effect will be approaching 100% reduction soon. One thing to note is that damage dealt via Soul Capacitor via Leech is not reduced by Arterial Cut.

It is much harder to achieve this so I simply did it as Sub.

Starting the fight as Sub:

Start by changing your Tier 6 Talent to Shuriken Toss and build a 46 second Slice and Dice on the constantly respawning ooze leading to Primordius' room.

Once you've done that open by Vanishing before you pull then starting with the normal T18Sub rogue rotation. Rupture, Reflection+Dance, build to 7CP, Evisc, Build 5CP reapply rupture, ambush for evisc etc.

When it comes time to use your second vanish make sure that you drop a Cardboard Assassin/Target Dummy or else Durumu will just reset additionally, best case scenario is to have Soul Capacitor up for this as well. Make sure to pool energy before Vanishing.
Combat Readiness before Light Spectrum phase since having 50% damage reduction will help immensely when paired with Feint.

Once all of your DPS CD's have elapsed survive until Shadow Dance is available again (make sure to pool).