The perception of challenge in a game is always contextual and based on prior experiences in the game space.
In the now lengthy Castlevania series, Order of Ecclesia should rank as the second best of the Metroidvania styles. First place should go to Symphony of the Night by a very slight margin and third to Aria of Sorrow. The funny thing about even saying one Castlevania game is better than another is that very little changes in any of them. Plots are almost non-existent and characterization even less so. You’re always there to kill Dracula or someone is trying to be Dracula. Like its sci-fi sister Metroid, you spend most of the game exploring a map or collecting abilities that let you explore more regions. The RPG system is a fairly basic leveling up routine with variety added only through how you collect abilities. The biggest difference amongst the titles is how each Castlevania game handles difficulty.
When I refer to difficulty, I don’t mean it in the abstract sense of the word. I mean the player’s quantifiable ability to ignore the game design’s desire to kill them through the use of health potions, overpowered weapons, being immune to damage, and general button mashing. Common sense indicates thst you should go soft on the player in this department while they learn the ropes and then eventually put your foot down and force them to actually play the game. Difficulty is then perceived because I have to change the way that I am playing the game in order to continue it.
Difficulty is probably the trickiest thing to get right in an open world game, and it is almost always the thing that holds back other entries in the Castlevania series. The designers don’t know what order the player is going to encounter things so there is no difficulty curve. The player might be at level 20 and a room full of zombies will be easy to kill, or they might be at level 2 and it’s going to be a tricky fight. Symphony of the Night’s solution to this problem was to make two castles. The first castle is similar to the design of Super Metroid in that you have to get items in a certain order to progress, albeit with a lot of wiggle room. Difficulty can be set to a curve and your stats at the time of a boss encounter can be reasonably predicted provided that you’re not purposefully gaming the system. The player also has the option to grind off the difficulty by leveling up and saving potions. Once you beat the first castle, a second one opens up that is almost totally open to explore, and the difficulty is ratcheted up to "Go Fuck Yourself" status. It is a great combination of two varying difficulty aesthetics because by that point you’ve learned the game’s mechanics, but there is still plenty of challenge left in the game.
Subsequent games in the series would have an awkward time capturing that formula. Circle of the Moon copied the formula of the second castle and is difficult to the point of unplayable. If you can beat the last boss in that game without cheating, pat yourself on the back because it broke me. Harmony of Dissonance backpedaled and put us back in the linear castle formula. While there are two castles in this game, because you’re moving through both in sequence it defeats the purpose of the whole setup. It’s just one big difficulty curve that you can break with potions and grinding. The linear castle in Symphony of the Night is a necessary evil that allows players to learn the game and enjoy collecting items. The second castle is where you actually have to deal with some challenging fights. As a consequence, Harmony of Dissonance falls into the same trap that many RPGs get stuck in: after about the 2/3 marker, you’re the ultimate badass and nothing is challenging.
Aria of Sorrow is remarkable because it actually pulls off the single open castle design and features one of the best 2-D open world maps ever created. One giant castle, one static difficulty for the whole thing, and it manages to stay reasonably challenging for most of the experience. It does this by starting off with a fairly linear setup and then opening up the lower and upper halves of the castle as you find key items that improve mobility. You can access the other two areas from multiple entrances so it maintains that feeling of exploration, but the difficulty is still broken up into three distinct levels. The first accessible section is easy, the second lower portion is a bit tougher, and the third one cranks it up another notch. It isn’t a perfect execution, and the game stops being hard about 2/3 through it, but it holds up better than the other titles.
The sequel Dawn of Sorrow just creates a totally open castle, and it runs face first into the main issue with all open world RPGs, the game is too easy. They don’t know what level the player is going to be when they get to an area, so once you start hitting the high levels, most rooms are still meant for a weaker character. With the exception of a few bosses on a linear path towards the ending, the game’s difficulty curve is all over the place. The only time that I ever had trouble playing was performing those awful binding spells.
Ecclesia uses transparent difficulty more than any other Castlevania game. All you have to do is kill a monster once and you can see their stats, weaknesses, and drop rates immediately. Stats include weaknesses to things like sharp weapons, blunt weapons, or spell elements. The game expects you to act on these because if you aren’t hitting a monster’s weakness, you aren’t doing enough damage to survive. This is one of the reasons that the Glyph system is such a clever solution to finding a way to enforce difficulty in an RPG. Since Shanoa just makes weapons materialize out of thin air, you never have to worry that the player has sold all their blunt or sharp weapons. If we say that the rule of thumb for transparent difficulty is making the player perform new move but that you always give clear instructions, Ecclesia is able to do this because its design allows the player to always keep their tools. Often the solution to a boss or level that is kicking your ass is to just experiment and see what weapons have more effect on it. This allows Ecclesia to be very firm in its difficulty levels while still being fair.
Ecclesia is simultaneously a return to Castlevania’s linear sidescrolling roots while still retaining a feeling of exploration. The majority of the game is spent going through small to medium sized levels with varying amounts of open and linear design. This means difficulty is paced on a steady curve and can have much more rigid standards. Remember that the perception of challenge in a game is always contextual and based on prior experiences in the game space. The reason the second castle in Symphony of the Night seems hard is because all the tactics and abilities that the player has been using in the first castle suddenly don’t work. Each level in Ecclesia offers a unique learning experience by changing the nature of the level space and monsters inside it. The Skeleton Cave forces you to use a lot of bashing weapons and slide dodges because of the jumping skeletons. The Somnus Reef level requires a lot of slow dodges underwater and a sharp cutting weapon for the sea monsters. I think that the game is harder because it is always making the player perform new moves. The game still allows you to curb difficulty with potions and other items, but money is much more limited in the game and items are very expensive. Unless you’re willing to do a ridiculous amount of grinding, you’re better off just learning to dodge effectively. Like any other game, with plenty of tinkering you can break the system after a lot of grinding but it seems silly to consider that a negative. People will make what they want of their games and difficulty can only control them for so long.
I never truly appreciated properly organized difficulty in the Castlevania games until I played Ecclesia. No other Castlevania game has gotten me to actually alternate between weapon setups despite it being a feature since Aria of Sorrow. I just picked a weapon and soul system that maxed my attack and charged in. I only adjusted my tactics to be more powerful. In Ecclesia, the damage discrepancy is so large that it forces the player to use the different attacks. By the end I found myself flipping through glyphs on the fly, shooting off a dozen arrows, dropping a light ball, smashing one opponent with a hammer, and pulling out the sword for a fleshy zombie. It felt pretty good to be executing complex maneuvers that fast and I only got there because the game made it that difficult.