re: Leviathan
Late to the party (but at least still relatively timely, since Ifrit isn't here as yet) but finally drudged up the will and the time to do this. Still annoyed I had to resort to Reraise strat for this, and even more annoyed that it was still a mess of RNG involved, but it's done. Leviathan mastered, 4 clears done, all over a minute (fastest was 1:06 minutes). Hugh, HUGE thanks to
@Jack-ums on Gamefaqs for his clear on Reddit and for giving me assistance.
Kain (LM1+DC LMR): R4 Impulse Dive, R4 Hurricane Bolt, Jump DMG+ (USB1/AASB/OSB), double lightning boost (50/50 lightning+ spear), 300 magia (ATK/HP/Lighting ATK)
Prompto (LM1+LMR1): R4 Plasma Shock, R5 Tempest Snipe, Acestriker (Glint+/USB/AASB?CSB), 400 magia (ATK/DEF/RES/HP)
Elarra (LM1+LM2): R4 Reraise, R4 Passion Salsa, DMT (USB1/AASB), 500 magia (ATK/DEF/RES/MND/HP)
Tyro (LM2+LMR1): R5 Entrust, R5 Wrath, MM (USB3/USB4), 300 magia (DEF/RES/HP)
Reks (LM1+LM2): R5 Stormspell Strike, R4 Dispel, Spellblade DMG+ (Glint+/AASB), double lighting boost (50/50 lightning+ sword), 300 magia (ATK/HP/Lightning ATK)
RW: Mage
Magicites: Ramuh (HP/Healing Boon), Quetz (HP/Dampen Water), Phoenix (Blade/Spell Ward), Madeen (Deadly Strikes x2), Madeen (HP+Healing Boon)
Odin accessories on everyone, naturally.
Technically Prompto had double lightning boost and was equipped with a 50/50 lightning+ gun, but in retrospect, I should have geared him for MND since he kept getting Stopped. HIs attacks did pitiful damage per hit, even at high chain count and +6 imperil. Lack of en-element really sucks for these fights.
Rough turn order:
Kain: Defend, Impulse Dive x2, US1, (Hurricane Bolt -> Impulse Dive x2 -> OSB) -> repeat sequence until turn 19 -> KO and get reraised -> RW to hopefully push to Phase 2, AASB after Turn 2 diffusion -> Dragoon Cycle until AASB runs out, USb1, OSB spam
Prompto: Glint+, Plasma Shock x3, CSB, Plasma Shock or, if at +6 imperil, Tempest Snipe spam until Turn 19 -> KO and get reraised -> CSB, AASB, Plasma Shock spam, refresh CSB at some point, Tempest Snipe spam, USB, Tempest Snipe spam
Elarra: Reraise, USB1, Passion Salsa, cycle Reraise -> Passiona Salsa until everyone one has Reraise -> wait for Turn 19 with full ATB -> KO and get reraised -> USB1, AASB, Reraise spam mixed with occasional Passion Salsas, USB1 when available
Tyro: USB3, Wrath x2, USb4, Wrath, Entrust kain, Wrath up 4 gauges, wait for Turn 19 with full ATB -> KO and get reraised -> USb3 ASAP after Elarra USb1, USb4, wrath, entrust to whoever needs it (Elarra is HP too low, otherwise save gauge for Kain to spam OSbs at the end)
Reks: Attack x2, Ramuh, Glint+ after Turn 6 diffusion, SSS spam until turn 19 -> KO and get reraised -> RW if still not in phase 2, otherwise wait for Turn 2 Roar of the Deep -> Dispel, AASB, SSS spam
So the overall goal is to get as close to phase 2 as possible before turn 19 Suffocating Waterburst Cannon without pushing phase. Turn 19 KOs the party, they get reraised with full ATB, and then it's push to Phase 2 ASAP, wait for diffusion and get Reks/Kain AASBs online, then DPS to the end. Reks just spam SSS forever until it runs out, I lose or I win, whichever comes first, and Kain does usual Dragoon Cycle (Hurricane Bolt -> Impulse Dive x2) while AASB is up, then switches to USb1 -> OSB spam to finish after AASB wears off.
The main issues I encountered were the following:
1) Getting as close to Phase 2 without going over is tough. HP% when? If you go too quickly, you end up having to reraise in phase 2 with shorter doom timers, and if you take too long, you end up with an additional Diffusion and more doom reduction in phase 1 rendering the whole exercise moot.
If still in phase 1 after both RWs, the only way forward is for Kain to do USB1 -> OSB spam and hope you reach phase 2 before Diffusion at Turn 24.
2) I had a weird thing happen to me. IN my first three clears, Turn 19 KOed the entire team and they all reraised at the same time. But in trying to get my 4th clear, I had a bunch of runs in a row where Kain mysteriously KOed first on that turn, then reraised,
then everyone else KOed and got reraised. I would nornally be hovering over Elarra when this happens looking to drop USb1 right away, because it is imperative that she go before Tyro does USb3. Otherwise, Tyro USb3 takes too long to get back online and if I'm still in phase 1, I eat Imperial Tidal Wave which slaps everyone for over 10,000 HP and I lose characters. But Kain getting back up first throws off the turn order, and by the time I cycle back to Elarra it's too late.
I did nothing different in my turn order to cause this than my first three clears. My subsequent 4th clear was just like my first three as well, with nothing changed, so I don't know why this happened.
I did eventually just start running with Kain first and cycling through the turns as fast as I could, which helped, though I ended up not winning for a bunch of other reasons on those runs (took too long in phase 1 or pushed phase 1 too fast).
3) The last 10% can get really hectic, depending on RNG. My first clear I won with only Reks and Kain still alive. Reks had run out of hones and was relying on normal attacks. Another run, Reraise spam under Elarra AASB saved me from getting doomed a second time at 0% HP bar, but everyone got back up with no buffs - no element, no hastega, and no gauge to do anything else. Reks managed to win with his last SSS which did 300x4, LOL.
So I'm really glad that was over. Though I'm irritated that I spent so much resources on the last Fest for this fight, and only about 25% of the pulls got me anything useful for it (Kain AASB came from the Jan 1st free 40 pull - if not for that, I would not have won). Hell, the 3 pulls I did on Kain SASB banner didn't matter much either (his Glint wasn't used, and his DC LMR did not proc often enough to really make a difference in my estimation, though I'm certainly glad I have it). I still had to resort to ghetto Reraise strat and RNG to win. But oh well. At least I'm caught up, Biodin notwithstanding.