For this achievement you need to rescue four allied soldiers from the four cells in Castle Prevant. It doesn’t matter if the prisoners are killed, as long as you saved them from their cells before they died.
As soon as you destroy the castle gates, and enter the castle the time limit starts. Make sure you save outside the castle, so you can go back and level or buy items if needed.
You will need Sunstones for this achievement; they can be bought in the castle or at the Nolaan General Store. You may also want to stock up on Miraculous Medicine and any other healing items you can afford. Leveling your characters will help as well. I would suggest you try for this achievement on the Easy difficulty, as the enemies will do significantly less damage making it much easier to survive.
The time limit allows you 4 minutes per soldier, so you will have 4 minutes to save the first soldier, 8 minutes to save the second, 12 to save the third, and 16 to save the fourth soldier. At the end of each of these 4 minute intervals a soldier is killed.
If ANY soldier dies before you rescue them you will NOT get the achievement.
A map including the location of all cells, keys, and treasure chests, routes 1 to 5 show where to go for each Cell Key and how to rescue each soldier.
(Castle Prevant - Map)
Note: You will need some Iron Metal and Marble for the fourth key. Iron Metal is dropped by the Order Servants make sure you get 1 piece at some point whilst going through the Castle. Marble is dropped by the Gargoyles, or can be more easily found in chest 9. If you have the "A Voucher" downloaded from the Xbox Live Marketplace you can buy both items from Genma.
Route 1 (Red):
Follow Route 1 to the southern room to find the first Cell Key, now head to Cell 1 and release the prisoner. Make sure to walk into the room after opening it.
Route 2 (Yellow):
Follow Route 2 to find a guard, kill him and use the cell key he drops to open Cell 2.
Route 3 (Blue):
Follow Route 3 to the mouse making sure to follow the map carefully to avoid any traps. Surprise and kill the Gargoyle by the mouse and then connect to Rico and speak to the mouse to get the third Cell Key.
Route 4 (Green):
Follow Route 4 until you arrive at the second dark corridor where you will need to surprise three gargoyles, the best way to do this is using Aya’s Ravaging Raptor connect skill, you don’t need to kill them after surprising them, just attack them to disable their traps. This is a good opportunity to get Marble if you haven't already.
Route 5 (Orange):
Once you have Edward in the party have him create the fourth Cell Key, then save your game on a new slot. Now head all the way back to the cells, and open Cell 3 and Cell 4, it doesn’t matter if your party is killed on the way back as long as Capell makes it.