How does cover interact with a Pact of the Chain Warlock with the Voice of the Chain Master Invocation

coverdnd-5efamiliarswarlock

I'm DMing for a group with a Pact of the Chain Genie Warlock in it, and he has Voice of the Chain Master. There was this one time when the party was investigating a nobleman's office and half of them got stuck inside when he showed up. The Warlock was one of the members that had already escaped. A very one-sided fight ensued so the Warlock, who was still within range to hear the commotion, decided to send the familiar back inside.

Now, Voice of the Chain Master says "You can communicate telepathically with your familiar and perceive through your familiar's senses as long as you are on the same plane of existence." The Warlock took advantage of this and argued that since he could see his targets (the nobleman's summoned minions) through his familiar's eyes, he should be able to target them with eldritch blast and scorching ray. At the time, I couldn't think of a reason why he wouldn't be able to, because I imagined the character lobbing bolts of force and fire from outside, and these bolts would then zigzag as required until they found the target the familiar saw, eating up a chunk from their 120-foot range because they'd have to somehow zigzag into the room through a chimney before even finding a target, so long as the spell attack roll was a success.

Now that I've had time to think, I'm wondering whether the whole zigzag thing would go against RAW because the targets where technically behind total cover, even if they weren't so from the familiar's perspective, since the spells originate from the caster, who was separated from the fight by a roof.

Also, I'm starting to wonder whether the Voice of the Chain Master is supposed to allow a Warlock to not have to keep using up an action to switch their senses with those of the familiar every turn, or just extend the range at which they can do so from 100 feet (as described in find familiar) to anywhere in the plane of existence, because in the latter case, he would have had to quicken spell anything he cast every turn (he has sorcerer levels).

Best Answer

Spells need a clear path to the target

This is on p. 201, PH:

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.

And total cover is defined on p. 196, PH:

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.

Directly meaning, no zig-zagging, or going around obstacles. The language of "concealed" is maybe not the best to chose, because a transparent obstacle would not necessarily conceal something, but it is clear what this means in the context of cover:

A target can benefit from cover only when an attack or other effect originates on the opposite side of the cover.

It does not matter if you can see the target, or not. For example, a pane of glass, or a crystal wall would both still block the clear path to the target. So, this would not have worked for the warlock.

There are a very few spells that must work without a clear path, for example the spot you teleport to with dimension door, but normally, for spells like Eldritch Blast, this won't work.

Find Familar action economy

The find familar spell says:

Additionally, as an action, you can see through your familiar's eyes and hear what it hears until the start of your next turn, gaining the benefits of any special senses that the familiar has.

Nothing about that is changed by Voice of the Chain Master, which says:

You can communicate telepathically with your familiar and perceive through your familiar’s senses as long as you are on the same plane of existence. Additionally, while perceiving through your familiar’s senses, you can also speak through your familiar in your own voice, even if your familiar is normally incapable of speech.

This only changes the range, and adds that you can speak through the familar in your voice, but it does not remove the need to spend an action to perceive through the familiars eyes.

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