When it is near death, it will transform into a more powerful form, resembling the Behemoth from Final Fantasy XII and will recover all of its HP and remove any status ailments, all while gaining higher max HP and more powerful attacks. It also gains the ability to use Thundara and Thundaga.
The player can wait for the Behemoth to turn its back and attack it to get a preemptive strike. Relentless Assault and Tri-disaster paradigms can be used to stagger it quickly. If the Behemoth is kept airborne using launch, it cannot transform until it lands.
Without preemptive attack, the party can deploy a Sentinel until the Behemoth is staggered. The party can also apply Curse on the Behemoth and Vigilance on the party and then interrupt the Behemoth with a fully offensive party so that it never gets a chance to transform even without being launched.
There is a Behemoth King to the right as the party enter Archylte Steppe on the south end, just after the Base Camp (the Archylte Steppe Northernlands is also an easier location for battling multiple Behemoth Kings). After killing this Behemoth, the party can run around, hugging the south east wall, past two Flan, and get close enough for the group of four Flan to see the party. The player can hop back up to where the Behemoth was, and it should have respawned. One can earn about 2,000 to 4,000 CP a minute this way.
A good place for end game grinding is in the Archylte Steppe Northernlands near the entrance to the caves. The battle is a three way between a Behemoth King and a Megistotherian and is always a preemptive strike. The player should first take out the Behemoth King before it transforms.
With a good party, the battle takes around 10 seconds with a reward of 6,600 CP, or 13,200 CP with the Growth Egg. After the battle, run up the hill a few steps past the Save station and they should respawn.
Behemoth is a beast mentioned in Job 40:15–24. In addition to mythological creatures, it is likened to elephants, hippos, rhinos, and bison. Metaphorically, the term behemoth denotes "an extremely large or powerful entity."