No bloody gear / Valiant Armor + Adamantine strats. So let's see what we can do to achieve this solo.
Equips (shown at 7:37):
- Fourth Book of Occult Philosophy, with Gathering Stars. This weapon is pretty wild. You can definitely use Reckless Magic, though magic potential will be high no matter what because of the +1 INT per combat skill activated. I had Gathering Stars on weapon to add AVD up.
- Robe of Ishtar, with Gathering Stars, for instant death nullification. Can also use Seraphic Garb. Can also use Robe of Deception for light element immunity, but will need to use Witch's Boots or Silver Charm for instant death immunity.
- Valiant Shield, with Gathering Stars. Best shield for Leon, with high AVD.
- The additional 50% spell damage with the Tiara headpiece is very nice. Has Narrow Escape, which plays a pretty integral part to this strategy, prevents getting one-shot and gives you a chance to recover.
- Bunny Shoes, with +20% AVD. Can sub with Witch's Boots, if you still need instant death immunity.
- Tri-Emblem, with Break Up. Adds Dark and Wind immunity (for Shadow Flare and Fohn Wind). Gives good stat boosts. Can sub with Gathering Stars on whatever accessory, if needed.
- Archangel's Bracelet, with Coercion. Lots of element resistances (covers 1/2 Water immunity), gives good stats, including INT, which is pretty lacking for accessories. Coercion is great to have to apply stat debuffs when shield breaking, works on all bosses.
This setup should give you a decent amount of AVD, but feel free to sub in an extra +20% AVD where you see fit.
In hindsight, using Robe of Deception and Witch's Boots for the light element immunity plus instant death immunity would have made this battle a little easier to manage. Whatever your setup is, 1/2 resistance to light element + at least 1 spell resistance buff is required to not get wiped by Meteor Swarm. I will say that the fast movement spell from Valiant / Bunny shoes isn't super necessary, since you're mostly casting spells and you can use Ointment of Veda to get fast movement.
At very minimum, all spell casting related combat skills, Surpass Damage Limit, Breaker, Heavy Hitter, Sidestep, and Overload should be maxed. Ideally, every combat skills should be maxed or as leveled up as possible. Consider disabling Backstab though, it maybe put you into a compromised position when you attack.
Formation is Tri-Shift 2, for ATK and INT Boost +60%, and Negate Enemy Resistances. Highly recommended for high-impact Extinctions, but feel free if necessary to use a more defensive formation. If you want to use dark element spells, the Negate Enemy Resistances bonus will be necessary.
For Assault Formation, they're all stat buffs. Rena on Reflection, Noel on Bless, Celine on Angel Feather, Ernest on Sandstorm. If you don't have some of these characters, I would use healing or skills the are break-focused.
First thing to do before anything else is use an Immunity pill. Absolutely necessary to cover stone immunity.
Next is to position yourself with your back against invisible wall. Absolutely crucial to not expose your back as much as possible. Then, apply your assault actions buffs.
Start applying some battle items that are helpful. Illusion Doll for extra AVD, Mental Potion for INT boost, Witch Powder if you need extra resistance. Mind Bomb can help mitigate enemy shield regen. You can use Revival Card too for a second chance if you die, though you'll need to reapply Immunity Pill and buffs ASAP after you're revived.
Extinction is probably the best spell in the game and is essentially the only spell you'll need here. You will see Extinction get more powerful as you keep triggering combat skills. I had Wounds and Ice Needles on R1 / L1, in case I needed some fast spells to help reduce enemy shield regen.
Your AVD after buffs should guard 90-95% of all non-magic attacks. If you do get hit, Narrow Escape will hopefully save you and give you a chance to heal (you may get unlucky occasionally, when you get hit twice in a row by an angel's Air Slash). Remember that your backside is completely vulnerable, no matter how high your AVD is.
It's very risky to dodge counter while both angels are still alive. You can easily get flanked or sandwiched. Sometimes you'll get a perfect dodge counter, but then the other angel will cast a spell right after, which can unfortunately stun you. Thus, lots of spell use. I don't recommend dodge countering while both angels are alive, unless you're super confident with your positioning or can shield break both at the same time. Once Gabriella is dead, then go all out with dodge counters if ya want, with the caveat that you need high enough HIT to not die from guard retaliation. Bless from Noel or Celine helps with this. Ultimately, it's best to play it safe by keeping your position optimal (reducing exposure to back as much as possible).