Here is the full list of all 33 Cassiodora trophies - there are 14 bronze, 13 silver, 5 gold and 1 platinum.
Obtain all trophies
Defeat Whomping Oak
Defeat Blackplume and Tailbreak
Defeat Pumpking Mike
Defeat Erik, The Brave
Defeat The Medusa
Defeat Kenzar, The Maleficent
Defeat Lord Necrom
Complete the Tutorial
Complete the Forest region
Complete the Desert region
Complete the Graveyard region
Complete the Cold Land region
Complete the Temple region
Complete the Volcano region
Complete the Underworld region
Collect all Cassiodora coins
Unlock all Agni skins
Unlock all Colden skins
Unlock all Luken skins
Unlock the Elemental Guardians
Complete all level challenges
Recover the life crystal at least 50 times
Achieve Rank S in at least 20 levels
Use all the Special Powers at least once
Collect all of Agni's ranged attacks
Collect all of Colden's ranged attacks
Collect all of Luken's ranged attacks
Pet your Elemental Guardian at least once
Finish the game in Apprentice difficult
Finish the game in Squire difficult
Finish the game in Warrior difficult
Finish the game in Knight difficult