Another round of fighting had begun. There were more champions in this round than in the last too.
This is how hunting usually proceeds. The fire ant colony will send more and more champions to get rid of him. So the longer the hunt continues, the more champions will appear and the more powerful they will be.
Of course, the fire ants won't start with the weakest champions. They will start with champions that they estimate are of the same cultivation as the enemy.
In the case of Arthur, they sensed that he had just become a third mortal coil cultivator so they sent their weakest fire ants to kill him. These weakest already have a power output of 1,000 units, so they were sure that the first champion would be able to get rid of Arthur.
But they were wrong. The first champion failed to drive away the enemy and even died. So they sent more champions that were also more powerful.