Could a Warlock with Ghostly Gaze and Sacred Flame attack through a wall? [duplicate]

Question

The Eldritch Invocation Ghostly Gaze allows the Warlock to see through solid objects out to 30' for as long as she concentrates (up to 1 minute).

For our scenario, our Warlock's nemesis has managed to evade the adventurers the warlock travels with by slipping into a panic room. The panic room is behind a 5' thick stone wall, and is 10' x 10', making the entire room within the 30' range of Ghostly Gaze while the Warlock is adjacent to the outer wall (or anywhere within 15' of it).

Weapon attacks are not possible as they cannot penetrate the wall, and many spells are also blocked by the wall as they involve a tangible effect traveling from the Warlock to the target (rays and such).

According to this question about targeting with line of sight but no line of effect, no spells should work. However, it seems certain that Sacred Flame would work as it specifically ignores cover. Is this correct?

Do the circumstances of the Ghostly Gaze spell allow any other spells to work (like Toll the Dead, that does not specify an effect traveling from the caster to the target, but simply "pointing to a target you can see within range")? I'm guessing that the answer is no, since the intent seems to be that there is always a requirement for an unobstructed path to the target unless stated otherwise (such as in Sacred Flame).

So, is Sacred Flame valid to attack the target? Are there any other cantrips that might work? Spells?

Answer 1

Spells require a clear line to the target.

This concept is covered extensively in two answers on this question: Can a spell be cast through (semi) transparent things?

Some excerpts.

From this answer:

In a podcast, [Jeremy Crawford] confirmed that you can't target enemies with spells beyond transparent obstacles because spells require a connection between caster and target.

From this answer:

The three spells all require you to target something. The things you can target are all bound by the rules on how to target things, and one of those rules is you cannot target someone behind total cover.

PHB pg 204, A Clear Path to the Target

To target something, you must have a clear path to it, so it can't be behind total cover.

If you place an area of effect at a point that you can't see and an obstruction, such as a wall, is between you and that point, the point of origin comes into being on the near side of that obstruction

"Total cover" is defined in the PHB, so this is a game term.

PHB 196, Cover

A target with total cover can't be targeted directly by an attack or a spell, although some spells can reach such a target by including it in an area of effect. A target has total cover if it is completely concealed by an obstacle.

So you cannot target a creature through a wall with a spell. You can, however, cast spells that require line of sight that don't target things, such as Silent Image and Misty Step

But what about Sacred Flame?

Sacred Flame's stipulation about cover only applies to the saving throw, not the targeting itself.

The target must succeed on a Dexterity saving throw or take 1d8 radiant damage. The target gains no benefit from cover for this saving throw.

Half Cover and Three-Quarters Cover provide a +2 and a +5 bonus to saving throws respectively. These are the benefits that Sacred Flame overrules. Based on that, my reasoning is that it does not override the targeting rules set in the PHB.

However, Jeremy Crawford disagrees with this ruling, saying that (transcript source)

There are spells that create exceptions to this rule about needing a path clear of obstruction. One cantrip [that breaks] this rule is sacred flame. Sacred flame is one of the low level spells that has this text: "The target gains no benefit from cover for this saving throw." [...] So, they're getting no benefit from cover [...] and that includes total cover. So sacred flame is one of the few spells that allows you to target somebody even if they're behind total cover. [...] You can be looking through the window in the tower and cast it on someone outside.

So officially speaking, yes you can, as that is the design intent of the rule. If you want to go purely based on how the text is written, then I would say no.

Answer 2

For most spells, no. For sacred flame, yes.

This question is a duplicate of: Can sacred flame target someone that is behind total cover?

TL;DR

So a solid wall counts as total cover regardless if the caster can see through the material.

Explanation

Jeremy Crawford ruled on transparency and total cover in this tweet and targeting requires a clear path as per the basic rules.

basic rule:

To target something, you must have a clear path to it, so it can’t be behind total cover.

tweet:

A solid obstacle, regardless of material, can provide total cover. A closed window counts. #DnD