Quite an interesting little lair this is. Judging from the old crates and structures lying around, it's likely the Umbraans used it as a storage facility. What I find most fascinating, though, are the Human structures scattered about the place. It appears the Umbraans were all too familiar with the infected substance, though their word for it translates into something that roughly means "solid sadness". Apparently it tends to collect in areas like this, with history. They've adapted the Ancient water pedestals as a tool to scare the infection off. Simply pray at the altars, offer a bit of water, and you will find yourself "blessed by the forest". I have a feeling this blessing is just a bit of Flow, but it seems effective in chasing off small amounts of infection.