Wyrm whose powers defies even the gods.Description
Yiazmat's basic attack is White Breath, which inflicts Stop. Cyclone inflicts non-elemental magic damage to all surrounding foes. Yiazmat is also the only unit to instantly kill one foe, which is done via Death Strike. Intercession is a new attack which fortifies all Espers on Yiazmat's side, same what Llyud's Quickening does.
Yiazmat is credited as the leader, so he isn't hard to find, especially since he is bigger than Tiamat and Elder Wyrm (which he resembles, but is in white). Yiazmat is accompanied by enemy Golems, Lamias, Cúchulainns, Raidens and Carbuncles.
When the battle is won, Vaan's sword, the Anastasia, is fortified, increasing its Attack, Mind, Stamina, Magick, and Strength by ten each. The battle can be repeated to enhance the sword further.
The recommended party is Filo, Penelo, Llyud, Kytes and Basch. Filo should equip the the Gold Earrings to protect against Stop and Kytes can equip the Goblin Pouch to earn Diamond or Zodiac Ore after the mission. The player can also deploy Vaan and Balthier for their powerful Quickenings, and Vaan is also a fast unit.
It is recommended to obtain the Summoning Gate before fighting Yiazmat, and there is only one. The recommended Espers to deploy for this fight are Golems (due to its resistance to the Stop status and highest Stamina), White Hares (for healing), Lamias, and Wyverns. Leviathan is a powerful Rank III melee Esper, although another one can be deployed as well, such as Titan.
The player should head to Platform 6 and clear out the Golems quickly, then move to Platform 5. Every platform will keep spawning three Espers and a Carbuncle. The Golems and Carbuncle also spawn in a bit, so the player should take them out as well. Next the party should move to the Raiden platform and kill them quickly because the Cúchulainns and a Carbuncle are charging at the party. When the Raidens are gone, the party can turn on the Cúchulainns.
The party can now advance on Platform 4 where the Summoning Gate is. The platform is guarded by two Lamias, Golems, Raidens and Cúchulainns with a Carbuncle. They can be wiped out with area of effect attacks, like Basch's Shining Ray and Kytes's spells. One should look out for the Golems that might have spawned back on Platform 6 who will come after the party. The player should capture the Gate once it's cleared.
After taking the Gate the player should get rid of Filo's Espers and summon the Leviathan and four White Hares for her. The others can summon the other Espers. Filo and her group should stay at the Gate and everyone else should move to the Raiden platform. Once the group is there and the enemies stop attacking, the group can move to Platform 6 where the Golems spawn and keep all of the enemies that come after the party at bay.
The player is now ready to attack Yiazmat. The player should activate Decoy Bit and Glide and advance Leviathan to the middle platform where Yiazmat and the four Carbuncles are waiting. Yiazmat will start attacking, but Leviathan is immunized against Stop by Filo's Gold Earrings and can take out three of the four Carbuncles. The player must not kill all four, as doing so triggers all the enemies in the map to attack at once.
Once the three Carbuncles are killed the player should try and change the direction Yiazmat is facing by moving Leviathan to the opposite direction so its Tidal Wave won't hit the last Carbuncle. The four White Hares can be moved behind it and have them heal Leviathan. Filo can run in with Defense, Power, and Speed Snare on Yiazmat. Yiazmat is very slow, which lets Filo zip and plant traps under him and fly away unscathed.
Leviathan can handle anything that comes his way, even Cúchulainns. The player should keep manually renewing Decoy Bit on it. When Yiazmat has only a little HP left the player can storm it and overwhelm it. Basch's Quickening is helpful here.