Considering their skills, it was pretty clear what their purpose was. They didn't even react to Luke's presence so that only confirmed things even more. In any case, Luke had to improve his way of thinking. He thought that more powerful opponents wouldn't use their heads against him, but it was clear that things were changing. It was quite worrisome given how they worked operating in such large scales... Luke probably would never go that far.
"Are they going to explode if we attack the fortress?" Luke asked.
"The possibility certainly exists…" Rina said. "However, even with his many, a chain explosion won't reach our allies. Nevertheless, the snake woman is probably trying to come, so we don't have time to be cautious."