I usually save the bosses until I've scouted the next level up because those mobs will be what raids you next.

Get some poison resist mead and start looking for a good swamp with crypts, which can be difficult because not every swamp has them. But even a small swamp might yield turnip seeds for better food. Look for the yellow flowers; they're very rare but could be anywhere in there. Once you have a general idea of how to get around the basic swamp creatures and have marked a few crypts on your map, then go for the Elder. You'll need him then.