The Cathedral
Map: The Cathedral
Prizes: 6 green mana, 6 blue mana, 3 Quartz Flasks

This one's easy: smash all the stained glass windows in the cathedral where the defiled alter is. Watch out for the spiders behind the back windows!

The Hidden Vault
Map: The Cathedral
Prizes: Staff of the Ovinomancer, Krater of Might, Mystic Urn

After going through the hidden passage beneath the cleansed cathedral altar, you come to a room with holes in the floor. Tap on the wall to the right to open a secret vault.

The Prisoner
Map: The Underhalls
Prize: Krater of Might

In the torture chamber, go into the cell on the left and press on the right-hand wall. When it crumbles, kill the prisoner (who just happens to still have his bow) and look at the wall. Carve your own message with the weapon of your choice to reveal a secret compartment and a Krater.

The Dark Mage's Bookcase
Map: The Tower of the Dark Mage
Prize: Force Cube

Go right at the beginning of this map, past the stained glass, and into a small study. Hit the green book on the shelf to swing it open so you can get behind it. The button just re-opens the shelf if it closes on you.

The Tube
Map: The Underhalls
Prize: Icon of the Defender

Just before you come up out of the water into the torture chamber, crank the wheel on the wall and grab that Icon.