If the challenge prohibited them from bringing their contract beasts and monsters, they might have refused to do the challenge at the Death Meadow.
Of course, the staff prohibited Ainsley from bringing her sacred beasts because it would be too unfair, considering that there would be no sacred beasts at the Death Meadow.
Even the highest-level monster wasn't as strong as Zilla.
The danger here only came from the variety of monsters and beasts, plus their overwhelming number and the place's terrain.
There were also a lot of mysteries related to this place which had something to do with the blood clan's battlefield back then.
The battle arena staff had arrived long before the challengers arrived, and they also got the insider news about how many people came to the Death Meadow today.