Change treasure:
Press [F9] to quick save the game when you find a chest. Lock pick or open the chest. Reload the game if you do not get a desired item. Open the chest again and the item will be something else. Repeat this until you find the desired item.
Super character:
Defeat Relican to join the Wielders Faction. An intermission sequence to start the next part of the journey to protect the ancient relics guarded by the Knights Templar will begin. After the sequence ends, the game will place you near a Way Crystal, which takes you to the La Perida’s Keeper Of Ways. Talk to the keeper and he will say his normal dialogue. Talk to him again, and a strange character changing screen will appear, where you can basically make your character super human, beyond the capabilities of even playing the game with it. The stats you can give them will basically allow you to give your character perfect stats, and give you the top level possible.