A lich listed in a WotC Adventure can cast wall of force.
More specifically the Archlich in Tomb of Annihiliation
We are trying to determine what the lich could do if it were to cast a spherical Wall of Force around itself.
Wall of force creates a barrier indestructable to physical attacks but also transparent.
According to answers in this question, spells require a direct connection from their caster to their target. Additionally, if we understand correctly, Jeremy Crawford has also ruled that transparent walls create Total Cover (i.e. he said that sight is not a requirement.) Thus, given that spells cannot target targets under Total Cover, even targets that are seen cannot be targeted with spells. Lastly, as described in the answer, the only spell that ignores cover is sacred flame.
Do these interpretations mean that everything outside of a spherical wall of force is under Total Cover to a creature inside of it (and thus untargetable with spells except for sacred flame) – and does that mean that not only spells but also Gaze Effects are ineffective as well?
Best Answer
The rules are unclear for the lich.
The Lich's "gaze effect" is this:
You correctly observe that this is not a spell.
The lich has to fix its gaze on the victim, which suggests a more intense version of just looking at them. You can look at someone through a glass window, but can you fix your gaze on them? It's hard to say.
For other "gaze" attacks, it's more clear.
There are other gazes that use different language. The Medusa, for example:
The Basilisk is almost identical:
Or the Nothic:
Note all of these explicitly require the monster to see the victim (and sometimes for the victim to see the monster) but not to interact with it in any other way. By definition, a transparent barrier can be seen through, so they work.
All of these are called "[Something] Gaze", so I'd take them as establishing a pattern that should apply to gaze attacks in general, but that's a little less solid.