The Fireball Level Path Is a path of levels off from the Great Hall in Dark Castle, Color Dark Castle, and will show up in Return to Dark Castle. It Consists of 3 Levels, Black Knight 1, Black Knight 2, and Black Knight 3.
This is the final level path, and it leads to the last level in Dark Castle.
The Black Knight, once defeated, has a Gargoyle drag you to the dungeon, you lose the Fireball and Shield and go up a difficulty. In Color Dark Castle once the Black Knight has been defeated on advanced, the screen fades out, and credits roll. Where as in the original version, you just keep playing.
In all the Black Knight levels, in random intervals Gargoyles show up.