The petitioner is a fugitive from Mt Bur-Omisace named Koqmihn. Now he lives at Dalan's place in Lowtown.
He tells you a legend about Behemoth King and asks you do annihilate him.
He has told you only a fragment of the legend and will tell you the rest after you have killed him.
About 1 590 000 HP
Resistant to Libra
Thundaga, Firaga, Blizzaga,
Ardor, Holy, Dakrga,
Paling, Magick Shield,
Behemoth King appears in Feywood in the last area just before Giruvegan, but to make him appear you'll have to kill everything in this area and in the former one (Ice Field of Clearsight and the Edge of Reason).
Behemoth has a lot of HP and what's worse it that you can't attack as you please, because his status varies between Paling and Magick Shield, so be prepared to change from time to time gambits from physical attack to magical and the other war around. Do not use the elemental magick, just use Scathe.
His normal attack (which alone is very strong) may cause Disease, but fortunately he also deals damage to the attacker. White Breath deals damage to every one in front of him and may cause Stop. To avoid that give those fighting in close range Power Armlets. Mage on the distance should have Sage's Ring and should cure his comrades when needed.
From time to time the enemy will cast Greater Barrier on himself and you just Dispel him right away. Somewhere around 30% his defense will raise.
After the fight get back to Dalan's place and talk with Koqmihn.
Bounty: 250 gil, 2x Bacchus's Wine, Behemoth King's figure in Sky Pirate's Den, hearing the end of the legend told by Koqmihn.
After you have talked with Koqmihn go to Mt Bur-Omisace, approach Wyrm's Snout [screen 1], unarm Vaan and hit it. A Wyrm Snout Plunder will fall on the ground. Examine it. You'll get 500 000 gil and Rod of Faith.