I'm not very good at platformers so forgive me if this isn't too helpful, I got to a little after you step of a cliff with a bunch of Guardgoyles on it then I got a game over. It looks like a nice Castlevania game! (I haven't played Castlevania so I can't any in-depth comparisons though)
-I like the artstyle! The little doom-like portrait of Not-Alucard is a nice touch! The UI is very pretty and fits the theme alot
-The little "stage name" text looks very nice!
-The owls are cute!
-Music is really good! It's definitely very Castlevania! (If it's Castlevania music being used as placeholder I'm sorry, I never played it)
-The graphics overall are very charming, I like the death animations and such. Only real complain graphics-wise is that it's sometimes hard to tell foreground tiles from background tiles, and some tiles feel a bit stretched out
Blood Knight is cool, but I feel like he should be doing more than just contact damage when the living armor looks like a lesser enemy and he throws axes
-I can't figure out what the blue fire stuff you get does
-Not-Alucard's feet clip through the floor when you walk
-I've heard a lot of game developers talk about coyote time, like you can still jump for a little bit after stepping off a platform. The game doesn't seem to have that. Are you planning or adding it or is it something the original Castlevania's also didn't have?
-Parallax breaks at the end of the first level/room/scene, since the foreground reaches its edge but the background keeps scrolling
-The hitbox on this one platform is a bit wonky, I fall through it sometimes 