The Mythical spells are the items used to reveal and enter the three Mythical towers. Every spell is divided in two parts and each part can be obtained in specific events. Once both parts of the same spell is obtained, they will be automatically combined into the complete spell.
A half Mythical spell can only reveal the door to the tower it belongs to, but the complete spell can reveal and unlock the door.
In Pipe Area, turn right in the first intersection and head right and jump onto chain that has a pig near it. Jump towards the small ledge on the wall. Use the spell to reveal the door to the Tower of Courage. This will allow Tomba to obtain the Glacier Boomerang.
Climb all the way up to the upper-leftmost part of Ranch Area to find the two Kokka Birds flying around. Walk up to the wall and use the spell in order to make the door to the Tower of Strength appear. This will allow Tomba to obtain the Torch Hammer.
Head to the Left-most part of the Deep Forest where huge blocks can be found. walk up to the wall there and use the spell. The door to the Tower of Wisdom will appear. This will allow Tomba to obtain the Doka Pin.