The Ghosts 'n Goblins games are hard. But if you're looking to jack up the challenge for some reason, you could find one of the many tombstones in the game and just start chucking weapons into it. Eventually

This... thing will appear, which will shoot a sparkly cloud at you, and if it hits,

Arthur gets turned into a frog for a few seconds, making him less maneuverable and unable to throw his weapon.

Yeah, come to think of it, I'm not sure why you'd want to do that on purpose.

And no, this doesn't work on the NES version of the game.