Operencia: The Stolen Sun

This achievement is story-related and unmissable, though it's probably the first major roadblock for a lot of players. I ran into a few issues on this level:

-Several mission-critical items are hidden behind illusion walls. It's not immediately obvious that these walls exist or how to spot them, but you can't pass the level without getting through them. The first you may see are in the west room with the little holes in the side of the walls. (Your characters will comment about shoving each other through them, before deciding they need to come back later.) The walls are on the right side of this room, and appear shiny and ever-so-slightly transparent. Simply walk through them to reach the other side.
-A second set of illusion walls are on the east side, at a dead end with some roots. This one is around the corner from a tomb you cannot open, which has room to slot 2 skulls on top to open.
-One of the door switches will give you a shock if you attempt to use it. To bypass this you need to fill your light vial, and next to the trapped switch will be the actual switch.
-Once you gather the 3 critical items and arrange them correctly (with the sun at the top, and the other elements below), the door to proceed will be open. If you interact with the door a number of powerful skeleton warriors will attack. Before opening the door i'd recommend saving and rest at the campfire just before the door. This fight can be tough, as the skeletons are immune to lots of your starting powers (such as sleep, poison, stun, etc). Be sure to eliminate all enemies and create all formulas you've found up to that point to max out your xp and unlock some big sweeping attacks.
-After beating the skeletons you're then in for the REAL boss fight. You should probably save and rest again before proceeding into the room and triggering this fight. The boss is incredibly damage resistant and has a huge pool of HP. Be sure to destroy her minions as she summons them, and eventually she'll stop bringing in reinforcements. She will occasionally raise a shield: you should take this opportunity to guard and recoup your AP, or heal your HP.
-The achievement is awarded after you exit the level (not upon beating the boss), so don't panic if it doesn't immediately appear.

This achievement is story related and unmissable.

Tomb of Reka is the third zone of the main story. You'll earn this achievement after completing it. You will complete this zone before you complete zone two, the Great Forest.