Bloodstained's difficulty

I would say : Harder than SotN.
I want a real challenge in this game. Not something impossible though.
I think we need to have a "chill mode" to enjoy the story and basically we should not face a terrifying challenge if we're just here to enjoy the lore. Two specific spheres but both present.
"Il en faut pour tous les goûts" like we say in French (~ all tastes must be pleased).

I already answered in depth but one thing I like in hard games (and for those who forgot I too want it harder than OOE) is when you DO stumble across a secret treasure room or lucky rare drop or something... I want it to feel like "*gasp*, thank goodness!" for first/second playthrus... not "oh yeah, cool, whatever"... that you feel when you get something extra that you don't feel like you really need.

I agree, they hit Order of Ecclesia just right and besides there's always grinding.

Multiple difficulty levels would be nice. Circle of the Moon is my favorite Symphony-style Castlevania so the harder the better in my opinion. But I realize not everyone likes games that difficult so the best option would be to have multiple difficultly levels you can select from at the outset.

Ok so, Castlevania difficulty is something I ruminate over often, so let me give my two cents.

SotN and AoS are piss easy. SotN gives you so many options between multiple pieces of equipment to pimp out your stats that removes most of the challenge from early on: gigantic knight enemies who deal billions of damage. You can simply outdo the enemy's stats by amassing equipment. AoS has some souls that are flabbergastingly good for their cost (Lightning Doll and Nightmare come to mind) and make the one instance where the literally game-breaking Claimh Solais is useless - Julius - pretty inconsequential. Potions heal way too much for their cost, so a single high potion can just get you out of any trouble. I honestly don't remember SotN's bosses a whole lot, but in AoS most of the bosses only had one or two attacks that worked in pretty predictable ways. Headhunter was probably the first real challenge in that game because he was mobile and had lots of different things going on between all the phases of battle.

DoS: Competent challenge. Some stuff is pretty tricky, like the final boss, Abaddon, and the Puppet Master if your weapons aren't optimized (which is good! Experiment with your equipment!!), but a lot of the normal enemies don't really leave a strong impression outside of damage sponges like the Iron Golem or Frankenstein, or monsters that deal baffling amounts of damage like the Cave Troll. The bosses all have lots of tricks up their sleeves, keeping the player on their toes at all times. Similarly, the most memorable regular enemies also have several different options, like the Malachi. Potions are a good deal less effective, but still matter because they restore decent chunks of HP.

PoR: See above, except enemies have a lot more options in general, which is a really good thing. Potions have a good balance in this game, being a bit less effective early on but also costing less.

PoR Hard Mode: bats and ghosts do 30% with each hit regardless of your level, bother this nonsense

OoE: Bats don't deal absurd damage, but everything else deals lots and lots of damage. I basically never used potions because this game is more based around Shanoa's mobility and dealing lots of damage. I like this though, it makes taking the initiative in battle really important. Blackmore is one of my favorite battles in the series because he deals so much damage and doesn't rely on gimmicks. Eligor is also a really neat gimmick/puzzle boss that doesn't end up being really tedious. My favorite part is that most of the game's enemies have lots of different methods of attack, especially the bosses. The Colossus boss in the mansion kicked my ass until I figured out his gimmicks.

The recurring pattern of this half asleep rambling is that enemies with lots of options make for the most challenging games. PoR is a really fun, solid game that I feel gets a lot of needless hate, but I can't stand its hard mode for simply clusterfucking the screen with objects and minor enemies that deal far too much damage. The parts in the Nation of Fools where you ascend past bone swings and Acrobat skeletons is actual challenge because you can move at a pace you feel comfortable with, killing what you feel like because the swinging bones work as platforms. Throwing ghosts and fleamen at the player in the pyramid level is just needless crowding and forcing the player to keep up with infinitely spawning enemies that can pop out of nowhere for attacks that can't possibly be reacted to is completely unreasonable and no fun at all. It forces the player to pick Jonathan just to tank hits.

Challenge isn't just about damage, it's about creating new situations where there wasn't a huge challenge before. The Medusa hallway in Castlevania 1 wouldn't be as hard if the enemies still did two pegs of health: you could just tank hits and stroll up to Death unopposed. My ideal difficulty curve would be between DoS and PoR, with higher difficulty settings focusing less on punishing the player and more about betraying the player's expectations by altering particular room's layout, enemy placement, or enemy behavior in specific rooms, especially if it takes into account the distance between save rooms.

Like Adventure: Rebirth did.

Bolded amazing idea.

It may seem counter intuitive at first, but the reasoning behind restriction, at least I would argue, is based on how players can relate to the experience. If a game mode is easy and has exploits/loop hole mechanics, restricting ones self to increase the challenge of a situation is a hollow victory. Sure, you may do it yourself, but who can relate to also doing it? Humans, by nature, are lazy. If an easy route exists, why bother with any other?

How the experience becomes relatable, what will fans talk about, and what were their experiences? These are the core questions I want to ask with respect to hard modes. If one sole variant of game play is exceedingly better than any other, especially when there are a plethora of items available, everyone's story will be "I used [Insert Unbalanced Item/Strategy Here], and it pretty much can solo the entire game, it's overpowered!". This makes the whole point of a hard mode stale, very fast. Furthermore, what is the point of a hard mode when it isn't generally that hard? It's such a contradiction to the entire experience itself!

I don't like item restrictions because it feels arbitrary and punishing for no real reason. I earned that super good item, why should I not get to use it how I see fit?

Now that I think about it I'm a glutton for Darkest Dungeon limiting the amount of items you can buy for different quests, so maybe I'm just a doof. In that case it's about stockpiling for specific missions though. Maybe if on harder difficulties the store (if there was one) would only allow you to hit say, five high potions in your inventory, so if you had five already you couldn't buy any more but could get them from random drops.

Easy: SoTN
Normal: Harder than SoTN, easier than OoE
Hard: OoE
Nightmare: Harder than OoE