Mourning A Friend

He was besieged by ten Disk Formation levelers. 

Even though Oreki was in the peak realm of Disk Formation, he is still, after all a Disk Formation leveler's

They were the same rank

It is not like a Divine Comprehension leveler fighting a Disk Formation leveler. Unless they were heavily restricted like Hikigaya who is maintaining the formation that keep this island united, any Divine Comprehension levelers could wipe out the floor with dozens of normal Disk Formation levelers.

Oreki had to use his all to fight these people. 

It is amazing that he even survived such battle. He had used many of his artifacts, most of which had been destroyed. He even had popped out all kinds of pills and uses all kinds of poisons to finally clinch that final victory. 

Their fight devastated the entire eastern region that it almost takes out the entire central eastern region with them. There are no trees, no grass only scorched earth.