Castle Warrior

The Atari ST version suffers from the same level 5 boss problems as the Amiga one. To beat him you should use a similar technique as in the Amiga version and hope for the best. At least the game acknowledges that the boss is dead even after he drains all of your energy at the very end, so you can advance.

Also in level 3 you don't lose energy for hitting the walls left and right, despite the blinking.