How to unlock.
This is not missable. As part of normal story progression, restore power to the 2,000 kW node northwest of the Alpine Stable power station. When you exit the power grid map, you will receive a message from Libertus. It tells you to meet a comrade at the gates. This initiates the "Keep Sleeping Kings Lie" story mission. After a short cut scene, you find yourself battling daemons. When you defeat them, there will be a story related cut scene and you will acquire the Oracle sigil unlocking the achievement along with an explanation of what sigils are. Location.
The Alpine Stable power station is located north and slightly to the west of Lestallum. You must restore power to it and to the node just north of it. Because it is in such close proximity to Lestallum, this achievement can be unlocked fairly early in the DLC.
"Keep Sleeping Kings Lie" is one of the simplest missions. There are no bosses. You only have to defeat a fairly large number of daemons. You can do so with regular and warp attacks. The daemons do not present a significant threat and do not require special defensive measures. When you defeat the final enemy, you will get the 'complete' notification. The story comrade you assisted will thank you and the game will transition to a cut scene where you acquire the sigil and unlock the achievement.Note.
There are a total of 13 sigils. The Oracle sigil must be acquired first as part of normal story progression. With one exception, the others are in tombs corresponding to the tombs where you found the Royal Arms in the main game. The 13th sigil is a reward for a scripted story event made available when you find the preceding 12. Not all 13 sigils were made available when the DLC was initially released. The version 1.0.0 Comrades DLC had seven of the thirteen sigils. The remaining sigils were made available in the March 2018 title update. Collecting all 13 sigils unlocks the following achievement: