The only viable light source will be a lantern that we received from Ophiuchus, the judges' team. The judges don't know we have it. Aside from that, it's pitch black; not even magical light can pierce it. The earth is more active then, so we should be prepared to evade if necessary.
We'll be exploring an area of the caves that contains an abandoned city with members of Hydra and Apus. The basic plan is to have a few people in a scouting role, to try and sense the keystone. If we find anything, someone shielded from its influence- Aoi or I- can retrieve it safely. We'll probably be with the scouting group, since we only have two lanterns between everyone involved. The rest of the people will be waiting as backup to provide distraction and cover after we take it.