Spiritual treasure
While spirit sense was mostly illusory, it could also be used to interact with physical objects. It was not a replacement for physical strength, usually, but still the ability to pick up or somehow manipulate items far away was very useful.
The process of interacting with physical items was broken down into a few simple steps so that beginners could focus on each individual step while they learned. First was, naturally, wrapping the intended item with his spirit sense. Then Lex would channel some spirit energy into his spirit sense, giving it the strength to harden temporarily at certain points, allowing it to touch physical items. Then, based on his control of his spirit sense, he could use the hardened portion of his sense to grab onto and manipulate the item as needed.