To get this you will need to collect
Shampoo / Super / Mega
Silky Cream / Super / Mega
Attract / Super / Max
Scimitar / Pike / Super Pike
Fireball / triple / flamethrower
Bubble / mirror / invincibility
Storm puff / Mega / Super Mega
Then, it'll look like you have two empty slots at the bottom. However, you are missing just one.
After completing the game, go to the Mayor who is in the Art Gallery and speak with him. He will give you the final relic, a Magic Tiara.