We’ve all been there: you find yourself in a dark forest, unsure of your surroundings, only sure of the wetness beneath your feet. You aren’t sure which way to run or if running is even an option, but you know that moving forward is the only way out. You want to scream, but the overwhelming oppression of your natural surroundings stifles any chance of exclamation. If only you knew whether this horrid place was classified as a bog, a fen, or a marsh, then you might have a chance at survival. But alas, without that knowledge, you are surely doomed. Better educate yourself, just in case.

For those of you who don’t know, each of these different swampland biomes have distinct characteristics that set them apart from other mires and everglades you may be familiar with. As an example, bogs are never complete without at least one wandering witch. As my grandmother always used to say, if you don’t hear a howling through the trees and dirt, you ain’t in a bog.

On the other hand, what is known as a marsh has completely different features and traits that separate it from a normal, everyday slough. For instance, marshes are known globally for their ability to break the laws of the universe and completely swallow a human being whole. We aren’t simply talking about people disappearing into marshes, but people being disintegrated and torn apart, down to their very cells, never to be seen again. Their matter will not be turned into something else, it simply has ceased to exist. This is one reason why marshes are often seen as the most dangerous of the various swamps found across the world.

Lastly, there are fens. Often seen as the bastard child of the entire enterprise, fens should be taken just as seriously as bogs and marshes. Originally described as ‘where evil and humidity join,’ fens are oppressively stagnant stretches of rivers, streams, or eddies that house the very worst this world has to offer. Beasts and gremlins of all shapes, sizes, and creeds can be found in just about any fen you come across. Be careful to avoid fens during the rainy season, as many a traveler has been lost and later found devoured by some unknown and unspeakable evil.

So, again, memorize these subtle distinctions for the next time you find yourself alone in the dark forest. At this point it’s less of a matter of ‘if,’ and more a matter of ‘when,’ so this is really in your best interest. Thankfully, we have a quick mnemonic device for remembering the differences.

Bogs are where the witches grow, marshes where the blood will flow, and fens are best left well enough alone, unless ye wish to be a pile of bone.

Hope this helps!

This article was written by Nathan Ellwood, who wants to tell you about this time he got lost in a mire, but that part of his memory wasn’t allowed to leave that horrid place. Follow him for more fen talk on Twitter @NPEllwood.