Book 6 Boss Guide
I’m sure there is a more optimal config to beat(or cheese) her, but while you wait ill tell you what i used to be Gloria, which was Lilith + Lady + Hecate.
Lilith and Lady are probably the most commonly used for their insane synergy and AP damage efficiency.
Lady for her AoE Exhaust(these don’t have to be leveled since their role isn’t damage you want at least 2 of them) and Mask damage(with relics), as it doesn’t count towards the damage counters.
Hecate, get her AoE SP healing ritual to gold and get the relic for it. Gloria will only ever damage your SP bars, its a fight of attrition so if you can stay alive you will outlast her while mask etc does their thing.
Hecate also has silence for her spells, she can essentially nullify her damage with Dark Ray when you don’t need to AOE exhaust her adds.
You’ll also need SP damage reduction skill(buffs) to help you manage the SP damage outside of Exhaust skills, and split spirit to turn red damage into purple, if needed.
Finally, if you have the skills that negates SP damage like mental barrier + cursed armor relic you can negate up to 10(6+4) SP damage block, you can then take the 15 SP damage punish several times(since you will be healing SP via ritual), you just have make sure you flip the bars correctly.