what is in the southeast corner if the island

There is a swamp on the southeast corner of the island.

Then a businesslike air animated him. "Ivan," he said to Rainsford, "will supply you with hunting clothes, food, a knife. I suggest you wear moccasins; they leave a poorer trail. I suggest, too, that you avoid the big swamp in the southeast corner of the island. We call it Death Swamp.