Here is the full list of all 16 Secrets of Arcadia achievements.
Complete the game with the Paladin
Complete the game without dying
Complete the game with every character
Complete the game with the Ranger
Find the portaits of the dungeon builders
Complete the game with the Warrior
Unlock every bonus chest
Find and open all standard treasure chests
Purchase every skill that is available to your character
Complete the game with the Mage
Complete the game in co-op mode
Defeat King Lameses
Defeat 250 enemies in a single playthrough
Find and defeat both of the Golden Knights
Collect 7,777 gems
Start a co-op game