So I was planning on making it into a Metroidvania but another commenter pointed out that the health draining mechanic discourages explorating for secrets so it would be hard to make it into a Metroidvania and I agree with them.
Instead, I plan to go in the direction of more of a rogue-lite game with a randomized map. However, so the player can take advantage of the blood they placed on the floor, instead of the map being randomized on each death the player can respawn in the same map a certain number of times to explore it further. Either I will make this a stat you can upgrade or make it so you can buy something that increases the amount of times you can go back to the map. I don't have the specifics down yet but I want it to be some sort of risk-reward design.
When playing on a fresh map, I was thinking that you could only start with one spell that you choose, and the rest you would find scattered throughout the map. More spells would be added to the drop pool as you level up.
I was planning on adding more movement spells and spells that interact with blood on the floor. For instance, I was planning on having the blood explosion knock the player around too, and have a spell that allows players to swim quickly through dried blood and damage enemies, and a spell that allows you to teleport to a blood spot and appear in an explosion of blood. Additionally, I was planning on allowing you to paint the walls with blood, by wall-sliding or by using spells that can do so, so you have more options on using these blood abilities.
I am still thinking about how I will handle overall progression but that is what I have thought of so far.
Let me know your thoughts, I would love feedback on these ideas!