https://castlevania.fandom.com/wiki/Symphony_of_the_Night_Bestiary

Dungeon Spawns Creatures and Rates

Nova Skeleton - Dungeon Hardmode Spawn (Low Spawn Rate)
Bone Scimtar - Dungeon Hardmode (Mid Low Spawn Rate)
Jack o Bones - Dungeon Spawn (Mid Spawn Rate)
Axe Armor - Dungeon Spawn (Mid Spawn Rate)
Ouija Table - Dungeon Spawn (Low Spawn Rate)

Graveyard Spawns

Stone Rose - Spawn (Rare)
Phantom Skull - Spawn (High)
Giant Skull Spirit - Spawn (Rare)
Winged Guard - Spawn Hardmode (Mid)
Ectoplasm Red - Spawn Hardmode (High)
Ectoplasm Blue - Spawn Hardmode (Mid)
Dhuron - Spawn (Low)

Corruption

Schmoo - Spawn (Low)
Scarcrow - Spawn Hardmode (Low)
Malachi - Spawn Hardmode (Rare)

Ice Caves

Frozen Shade - Spawn - (Rare)
Fish Head - Spawn - (Low)

Hell

Lossoth - Spawn (Low)
Hellfire Beast - Spawn (Rare)

Boss Spawns

Orlox - Spawned Using Fresh Meat In Hell (Disables All Hell Spawns and Running Away vertically causes instant death

I hope this inspires :D Also incase people dont like Castlevania you should make it so you can toggle Castlvania mods on or off.