The core of the arena sensed the key and had to accept it. It needs the key before it can join the full network of arenas. So it opened itself despite knowing that he is there waiting for this exact chance to pounce.
Soverick pounced at the vulnerability that appeared. He dug in and tried to break the defense in one fell swoop. His efforts were not enough. The other arena spirits helped in resisting him. He only got halfway through. His progress was delayed by their defense so the key left him behind. Then the vulnerability closed up faster than he could take full advantage of it.
He sighed and said to himself. "This will have to do for now. One more and I'll get my price."
