The hidden level is in stage 5. After you beat the first boss, a
jumping demon creature, you must go through the doors to get to
next screen. There will be two paths, up and to the right. If
you go to the right you will find an empty room, so don't bother.
You must go straight up, stay to the right. There will be an
opening in the wall leading to the next screen. The next screen
will have two bats hanging on the ceiling and a platform below
them. Below this platform is another smaller platform, which is
over a hole in the floor. Jump down this hole. While falling you
will see a candle, whip it.
After you get the 1-up candle, you will land on a platform. On
this platform will be a white candle. Whip this. Then proceed to
get off the platform. Do not exit the room. The floor below now
will have disappeared. Jump in it. This will lead you to the
Hidden Level in Level 5.
Here's some passwords for your playing pleasure.
3 Axe, Cross, Space, Clock
4 Clock, Space, Dagger, Dagger
At the password entry screen, enter Meat, Candle, Candle, Meat.
This takes you to the last level and gives you all the items and
soul weapons on the Light Mode difficulty.