So, earth and water so far. As well as whatever got in through the broken upper levels. [He traces over the spots reported to have been damaged. How much of the knowledge there is now lost? But that isn't their job.

Their task is to secure the ruins so others can salvage what they can.]

Since we're on clean up duty, temporarily blocking the gaps anything could come in from wouldn't be a bad idea. If we're dealing with the cave system too forming a blockade just before the section they meet would be ideal. We can use whatever is too broken to be repaired.

They can remove it and melt it down later.