The good:
The moveset and passives are quite unique, with the HP bar passive ability being quite helpful for a character based on fast play so you can keep score from rings up more easily.
The bad:
The sprites jank around constantly, and the fire effect in Furnace's running animation is cut off. The CSS info is also badly put together.
Suggestions:
I'd advise just making Furnace fully 2D like Earless so janky sprite issues do not happen. There should be an indicator that Furnace can do the wall jump, such as a flame effect replacing the smoke particle effect Furnace usually gets while moving.
Replace the status bars at the corner of the screen, they just take up space.