This assignment you get from High-Chief Zayalu on Elderknoll in Jahra.
About 20 000 HP
Resistant to Libra,
Vulnerable to Holy,
Slow works on him
You can find him in dead end in Henne Mines. At the beginning it's good to slow him down. His attacks are Doom, Aerora - a black magick spell with the element of wind damaging everyone in range. Here except for Ixtab you'll find some Redmaws - kill them first so that they didn't interrupt you in the fight.
Bounty: 1300 gil, Ether, Soul Powder (2241g)