Excerpt from "Traveling the Beautiful Borgo Pass"
Although one wouldn't normally consider marshes to be beautiful places to visit -- they're full of nasty little creatures like mosquitoes, leeches, fleamen, jersey devils, and gnats -- there are some benefits to be found in the wonderful marsh on the grounds of Castle Dracula. Having seen the restorative properties of the mud in the Marsh (many corpses have been dumped into the murky waters and been kept well preserved), the Dark Prince elected to set up a Spa and Resort to tap into these preserving muds.
Make sure to book your reservation early as space is limited at the marsh. Only so many bodies can fit in at one time, and slots to attend the spa are booked out weeks in advance. You really do owe it to yourself to see the mud, to feel it slip over you, dragging you down to a relaxing sleep.
About the Marsh:
Marshes are, technically, a term used in the series to encapsulate marshes, swamps, and bogs. The term gets is name from the first appearance in the series: the various marshes in Castlevania II: Simon's Quest These locations -- Belasco Marsh, Denis Marsh, Joma Marsh -- are nasty places to visit, packed with mudmen and other evil beings, and filled with murky, deadly water that damages hero Simon Belmont as he walks through it (prompting the used of invincibility laurels). Naturally, these locations exist outside of Castle Dracula, as does much of the Romanian countryside in Castlevania II, but it did set the tenor for the rest of the series.
The first official marsh stage in the series came one mainline game later in Castlevania III: Dracula's Curse. Stage 4 (Route 5) of the game, the so-called "Murky Marsh of Morbid Morons", is a shorter stage packed with foot-sucking mud, along with mud men, bats, and frogs. The stage culminates in a battle against the Giant Bat (one of two in the game, depending on the route you take), before the stage quickly ends.
Following that, we then ventured into the swamps of the Transylvanian Wilds in Super Castlevania IV. This second stage of the game is broken up into a couple of sections, with a forest leading into a short cliff-side expanse, before leading into a longer section in the swamps. Frogs, crows, and une dot the landscape here as Simon once again has to traverse bridges and muds to reach the far side of the murk. There he'll face off against Medusa before heading off towards the aqueduct that marks the back third of the stage (and the stage's exit).
Between Super Castlevania IV and the next mainline entry a remake of the original Castlevania marked our next appearance of a marsh. Castlevania for the Sharp X68000 (named Castlevania Chronicles for its later release in the West) featured an expanded set of stages, including some brand new additions to Dracula's Castle. The marsh was part of the new Block 3, taking up Stage 8 within that block. It was, once again, a murky, mud-lined area with nasty creatures living inside.
Officially the next new game, Castlevania Dracula X: Rondo of Blood then had our next appearance of a marsh. Built as part of the alternate Stage 3', "Release from the Thirst for Blood", the marsh comes after the opening area of the stage, the cemetery. After moving through some lower sections of the cemetery, which did have muddy areas, the murky waters take over in the back half, as part of the climb and final pass through the stage. This ten leads to a battle with the Minotaur before the heroes join back up with the man path the Stage 4. Interestingly, if the heroes take the secret exist out of the cemetery (which is also the fastest way through the game) they won't see the Marsh and will, instead, confront the Dogether deep below.
It would be some time before we saw a proper swamp again, with the games largely moving into the castle's interior for multiple games. We finally revisit the murky dank waters in Castlevania: Order of Ecclesia. The marsh, Argila Swamp, is one of a couple of very straightforward "hallway" stages, leading heroine Shanoa across the countryside to her next unlocked destination. The swap here is filled with the usual assortment -- une, owls, and other plant creatures -- but no boss.
And finally we have to venture into the alternate history for the series to find a swamp over in Castlevania: Lords of Shadow. Marking he third section of Chapter 1, the Dead Bog is filled with deadly waters (making it more akin to the bogs of Castlevania II) and goblins. The keep point of interest here is an old ruined church which contains the Hook Tip, a necessary whip attachment that allows hero Gabriel Belmont to rappel and swing from his whip.
The Murky Marsh of Morbid Morons in Castlevania III: Dracula's Curse
The Transylvanian Wilds, marsh section, in Super Castlevania IV
Release from the Thirst for Blood, swamp section, in Castlevania Dracula X: Rondo of Blood