This page of the guide to Lost Ark explains where to find one of the Soul Left in X-301 quest items - the Eye Sensor dropped by the Secret Base Guard robot.
A Lighthouse for the Soul is one of Lost Ark's quests found on Starlight Isle. Progressing it leads to the Soul Left in X-301 quest on the Facility X-301 island. You must head there and get some items dropped by encountered robots. One item, however, is slightly more difficult to obtain: the Eye Sensor. It's dropped by the Secret Base Guard mini-boss who spawns on the second bridge from the north, on the west side of the island. It respawns every 5 minutes. You should kill it as soon as possible, as it can quickly escape to the other side of the island with its jetpack. It's not guaranteed to drop the Eye Sensor on your first try.