For each stage there is a breakable wall, that contains Thor's Hammer.

Thor's Hammer adds a blue aura that, when you take damage, is released as a spread of 8 radial projectiles. These kill most enemies on contact. If you obtain another Hammer while you already have the aura, it will grant you score instead.

At each location, there is a small rusted sword, embedded into the ground nearby.

To access the Hard stages, you must first collect enough consecutive chests, without being hit. Once you have enough, you will be granted warrior spirits. At the end of each world, take the top path where the statue stands. Each warrior spirit you have, allows for a single try at hard mode.