Darkonium is found in the blue chests that are scattered around the islands. (These are in the order I found them)
- Chest on Xeroph Isle at the bottom of the "bowl".
- Chest at the end of the First Shrine on Xeroph Isle (before the "final" door).
- Chest in plank maze on Palaish Isle.
- Chest is inside a tunnel concealed below the plank maze on the path towards the shrine.
- Chest at the end of the Second Shrine on Palaish Isle.
- Chest on Infern Isle at the end of the spiral path on the north side of the island.
- Chest in the Ruins (near the beginning) on Celeste Isle.
- Clear the C rank Tourney at the bottom of the Xeroph Isle "bowl".
- Chest on small island off of Infant Isle.
- Chest on small island off Celeste Isle, end of 3rd shrine, before boss.
- Receive from question Guy on Infant Isle, after 6th or 7th question is answered.
- Chest at the top of one of the columns in the jungle of Fert Island.
- Chest located next to the shrine door on Fert Island.