GAUNTLET II

While adventuring, find a treasure chest and make sure you have a key.  Hold
down INSERT when you open the chest.  Release INSERT, and hold the joystick
down.  Now the HELP key will give you 5000 health points.

If that doesn't work then try the following

When you open a treasure chest hold down the 'HELP' key, then when you
open a second chest hold down the 'INSERT' key.  A golden cross should
appear, collect this and your health points should rise by 50,000.
You will also have super shots for the remainder of the level.

You can also try this

To avoid tricky levels, pause the game and wait for three minutes.
Press fire and all the walls turn to exits.  This happens anyway, but
if you pause the game, you don't lose energy, and won't get attacked
while waiting three minutes.