The Crimson Depths

"What's up my dear Journey Junkies. I'm a bit roughed up, but my expedition team and I returned home safe. We did find that abandoned vault that's been lost to time. Though the journey certainly was tough, even for the elves who are native to the Underdark. We had to trek through an area called The Crimson Depths to get there and, I may be a brave soul, but I'd rather not return anytime soon. I can still smell the mold and rust the permeated the air." - Part of a travel blog post from Birki Kroon  

Deep in the southeastern Underdark is a place few dare to traverse. The Crimson Depths is a series of caves, tunnels, and steep drop offs that lead to a dead end where an abandoned vault is located. There are no settlements or attractions. Local officials strongly advise people to stay clear. A few research teams have made charting and observation attempts over the years. 

What Lurks Below

Gas pockets and spore clouds aren't the only danger hidden among the depths. There are numerous creatures that have adapted to living in such hostile conditions. Occasionally brave groups of criminals have set up base to protect valuables. None have stayed for very long and either perished or moved on to another location. 
Scientists and explorers have discovered: 

• Dog sized scorpions whose claws are strong enough to smash some rocks. They fortify their venom by eating some of the toxic molds off the cavern walls. 
• Pools of acidic water that are slowly eroding through the earth. 
• Large worms that eat through the rock. 
• Small worms that produce metal threads instead of regular silk. 

Type

Underground / Subterranean

Air Quality Advisory

Health officials warn that anyone who does travel through the depths absolutely needs to wear a high quality respirator. Due to a high concentration of mold and fungus, the air is saturated in spores. Toxic fumes also get released into the area from deep gas pockets that burst through cracks in the ground. 

Soil and Rock Composition

Researchers managed to analyze what makes up the terrain of the area. High concentrations of iron and red algae contribute to the depths deep red orange hue. There are large colonies of anaerobic bacteria and other microorganisms that live in the patches of dirt that were created from the breakdown of the rock.