The enraged Beast Goblin King's power had been increased massively after it lost an eye and became enraged, however that wasn't the only thing that Adam had to be worried about.
The powerful aura of the enraged Beast Goblin King awakened the other three Goblin Kings that were slumbering in their towers and that was the start of the real battle.
Luckily for Adam, the other Goblin Kings couldn't leave their towers unless they were attacked first and were mysteriously bound to that rule, but it meant that they were alerted of the presence of an enemy and also gave them the chance to gauge Adam's power by sensing his aura from their towers.
The Magic Goblin King was also able to observe the battle clearly from its tower using its spiritual sense along with a clear glass orb that it held in its left hand as everything wasn't looking good for Adam.