D&D 5E Ghostly Gaze: how does it *really* work?

[Dausuul]

I would rule that Ghostly Gaze provides a completely separate form of vision, which works alongside your normal vision. They do not block each other but also do not interact.

So, in the tower with the shutters open, you can see 1 mile through the windows, and 30 feet through the walls, floor, and ceiling. If you close the shutters, your vision is now limited to 30 feet in all directions.

 

[jgsugden]

I've not had a Warlock take this invocation that I can recall, but based upon the language:

...you gain the ability to see through solid objects to a range of 30 feet.

This line tells us that we can see through objects to a range of 30 feet. Objects within 30 feet do not block our line of sight. The next 2 parts establish the darkvision of 30' and the concentration requirement.

...During that time, you perceive objects as ghostly, transparent images."

Note that there is no range limitation on this statement explicitly. However, we can assume it was intended to apply to the 30' range because saying that you perceive objects as translucent with unlimited range would effectively negate the 30 range in the first sentence.

While this vision is in place, you perceive objects as ghostly and transparent. That means you perceive that light can pass through them and things on the other side of them can be seen clearly - regardless of how far beyond them they are. I had not considered the implications of this before, but I have to agree that at the top of your tower example, you'd be able to see for miles. Essentially, you replace everything around you in a 30' radius with glass (lit with darkvision light).