Chapter 113: Their story - Hera
While it was hidden from all parties involved, the main reason the beast broke down at the rate it did was due to Tasha spying on the area with her spirit.
Ultimately, the beast craved a soul to fix the problems that came along with fusion. It was also the reason the beasts of the choatic era always devoured all those that came across their paths.
What they thirsted for was the soul, not the flesh however the flesh was a welcome addition.
The close proximity of a soul based creation, Tasha's water spirit to the battlefield meant that the beast could sense it, the way it locked down the position by emitting nether pulses meant that it was aware of the exact location the spirit was.
On different occasion during the course of the ballte, the beast did try to move towards the location it knew the spirit was hiding, but Ariad managed to steer it away, instead moving the battlefield further inland.