FFXII: How to Kill Yiazmat

HP: 5,0112,254

Immune: All Status Effects
Elements: Weak to Dark. Absorbs Holy. Half damage for rest.
Technick Vulnerabilities: Expose, Shear

Abilities
White Breath- Area of Effect - Ice damage, chance of Stop
Stone Breath - AoE - chance of Petrify
Regular attack - physical + chance of Death
Rake - fast, 2x damage
Cyclone - Wind damage, chance of Sap
Deathstrike - Instant Death, single target, 100% unless target has Shell
Growing Threat - Doubles Level
Reflectga - Uses on Party

--Adapted from: Rodney Tilger's FFXII Mark Hunt Guide

Division of Labor:

Fighter: Vaan/Basch

Masamune

Hit hard and often

Healer: Ashe/Penelo

Orochi/Ninja weapon with Dark

Heal and recharge MP

Both: Fran/Balthier

Tournesol/strongest weapon*

Back up both

Tactics:

1. You'll need a full pack of Chronos Tears, Remedies, Gold Needles, Phoenix Downs.
   
2. Now's the time to use those Elixirs, Hi-Ethers and Megalixirs you were saving for a tough battle.
   
3. Be ready to switch gambits when you run out of one of the above.
   
4. Lower Yiazmat's defenses with Expose for a couple bars at start.
   
5. ALWAYS have someone attacking. Yiazmat doesn't do Deathstrike very often while he's being hit.
   
6. Keep characters bufffed with Shell, Haste, Bubble, Protect. Add Faith and Bravery when possible, keeping in mind #2.
   
7. Try to stagger buff spells so you're not having to do a bunch at once. When all 3 characters are attacking, that's a breather moment -- cast one buff.
   
8. Ignore the traps. They're just needles, 20-30 HP damange.
   
9. If everyone's keeping up, don't worry. But if you start running into trouble, move a fallen character(s) to the back in the Party Menu, turn OFF the Bravery and Faith gambits, bring in replacements, get things under control, have healer use Arise + L1 to target fallen member, bring fallen member back in to be re-buffed. That way backups are always buffed, and you never have two people effectively out of action (one KO, the other reviving the KO).
   
10. If you're in trouble, run back down the stairs and into the next room. Yiazmat will not regenerate HP while you're offscreen. Don't wait in the corridor -- he could COMPLETELY RENEW (I found out the hard way).

See below for my Yiazmat Battle Gambit Set-Up.

Etymology

Its name is a reference to director Yasumi Matsuno's nickname (Yazumi Matsuno). The additional "i" in Yiazmat's name is not present in the Japanese version, likely being a localization decision to associate it closer to "Tiamat".

Farewell to a Legend?

The title of the hunt is "End of a Legend", a reference to how he had to leave the company before the game was complete and the story that Montblanc tells is a reference to how the development team felt about him, albeit with a different end.

Another theory is that Yiazmat is the game's depiction of Matsuno, and the moogles being the development team and their master being Square Enix. Matsuno prolonging the game killed Square Enix "financially" and the development team felt Matsuno had to be slain as retribution for his actions. The hunt title basically says "Farewell" to a Legendary monster - Yiazmat - both being an homage and an insult to the director.