Yamata no Orochi/Labyrinth of Chaos

A legendary monster from ages ago, closer to her peak of power.

Gets 3 actions a turn.

Biograph
One of the superbosses in the Labyrinth of Chaos, Yamata no Orochi is only encountered as a floor 100 boss.

Attacks

 * Attack - One Foe
 * Snake Punisher - All Foes, Physical
 * Draining Light Talisman All Foes, Auto Hit, Holy Attribute, Holy Weak 100%, Ascension 10%, 3 Turn Cooldown, 15 MP
 * Greedy Dark Talisman One Foe, Auto Hit, Dark Attribute, Dark Weak 100%, Death 75%, 3 Turn Cooldown, 12 MP
 * Sacrifice Tasting - One Foe (X8), Pleasure Attribute
 * Eight Head Assault - One Foe (X8), Pleasure Attribute
 * Head Bind - One Foe (Luka), Bind 100%
 * Unending Licking - Rape X 8
 * ? - Random 8 Foes, Physical, 3 Turn Cooldown
 * Blazing Inferno Breath - All Foes, Auto Hit, Fire Attribute, Burn 10%, 3 Turn Cooldown
 * Bad Breath - All Foes, Auto Hit, Poison/Blind/Silence/Confusion/Sleep/Paralysis 50%, 3 Turn Cooldown

Strategy
Warning! If you haven't been making use of Waning Moon Dance or characters with Hasted Skills, Yamata No Orochi is your wake up call. First of all, lets address the main issue: She gets 3 actions a turn. No matter WHAT you do, she'll most likely wipe the team, stomp on your corpses, and then salt the earth for good measure. Her fight is not one that you take head on unless you're massively over leveled. Thus, the proper way to fight is to open up with Waning Moon Dance on someone with Hasted Dance and pray that she doesn't use her Blazing Inferno Breath/Draining Light Talisman. Then, while you still are protected from most of her attacks, try and either put her to Sleep (A good 75% chance to do so) or Petrify her (Risky, at 25%). You could also try your hand at Blinding her, but any attack that she has that would be affected by blind is rendered null by Waning Moon Dance. Or, for the daring, allow Luka to be captured by Head Bind, with Waning Moon Dance active, he'll never take damage from Unending Licking. The downside is that she'll use it 3 times, each hitting 8 times, for 24 messages of "Luka took no damage!", which can get annoying if you don't have skip text active. For a final warning, Bad Breath, despite not dealing damage, is arguably her deadliest move. One a simple 3 turn cooldown, it can inflict 6 different status ailments, 3 of which will prevent a character from taking their turn. Either stack resists against those 3, or try and lock down Yamata no Orochi before she can use it.

As for damaging her, she's neither immune to any element nor weak to any element, but Ice is your best bet. Combine this with her 4 different ways to apply Slayer (With Giant giving the strongest, at 200% bonus damage), and you'll quickly burst though her health. Of course, you could always try to insta kill her if she falls asleep...

Check here and here for detailed information on all the superbosses and everything you can make use of to defeat them.