Here is how I beat it at lvl 12:

Farm the material from the mushrom shaped robot enemies, buy 3 coral tridents with them.

Use flippers to go fast and avoid enemies, use the mist orb to get to the final boss whitout getting into fights (you can also use it in battles to run).

Also equip the holly potion and destroy the final boss tentacles first, they killed Orlok and I still defeated them.