We were fighting Vecna himself, and at one point had a *[prismatic wall](https://www.dndbeyond.com/spells/prismatic-wall)* up between us and Vecna. The *prismatic wall* says it creates "a vertical, opaque wall."

Vecna's powers include truesight, and presumably x-ray vision as well (since the artifact *Eye of Vecna* allows its bearer to use x-ray vision), and the DM thought Vecna would be able to see through the prismatic wall and target us. A *[ring of x-ray vision](https://www.dndbeyond.com/magic-items/4738-ring-of-x-ray-vision)* states:

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> While wearing this ring, you can use an action to speak its command word. When you do so, you can see into and through solid matter for 1 minute. This vision has a radius of 30 feet. To you, solid objects within that radius appear transparent and don't prevent light from passing through them. The vision can penetrate 1 foot of stone, 1 inch of common metal, or up to 3 feet of wood or dirt. Thicker substances block the vision, as does a thin sheet of lead.
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So can someone see through a prismatic wall using truesight/x-ray vision?
['https://rpg.stackexchange.com/questions/201346', 'https://rpg.stackexchange.com', 'https://rpg.stackexchange.com/users/30992/']
Neither effect allows you to see through a Prismatic Wall
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Prismatic Wall has this effect:

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> A shimmering, multicolored plane of light forms a vertical opaque wall
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### Truesight

[Truesight](https://www.dndbeyond.com/sources/basic-rules/monsters#Truesight) allows you to

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> see in normal and magical darkness, see invisible creatures and objects, automatically detect visual illusions and succeed on saving throws against them, and perceive the original form of a shapechanger or a creature that is transformed by magic [...] see into the Ethereal Plane
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It does not allow you to see through an opaque barrier. While you can see into the Ethereal Plane, what you are looking at is not not *on* the Ethereal Plane, and if you could see them *from* there does not matter, as neither are you.

### X-Ray Vision

X-Ray Vision (as in the [ring](https://www.dndbeyond.com/magic-items/4738-ring-of-x-ray-vision)) allows you to

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> see into and through solid matter (...) To you, solid objects within that radius appear transparent and don't prevent light from passing through them
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The wall is not a solid object or solid matter, as it is made of insubstantial light that you can walk through, which you could not if it were solid. So X-Ray Vision does not allow you to see through it, either.

### Vecna

Could you use either as a player character if you tried to look through a Prismatic Wall? No.

Could Vecna? Not by the official stat block that has been printed in the [Vecna Dossier](https://www.dndbeyond.com/claim/source/vecna) (where he does not even have X-Ray Vision, as he does not have the Hand or Eye of Vecna, he is said to be questing for them). However, the lore section there states that

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> More recently, Vecna decamped to the Outer Planes, where he grew so powerful that he became a god.
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And there are no printed rules for gods. Even without invoking their right to overrule anything, the DM can rule that he could see through the wall. And even for pre-apotheosis Vecna, they of course can rule so, because it's Vecna and because of their right to overrule. Your DM in any case did rule so, so your Vecna could.
RAW, vague.
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True sight and x-ray vision could either be *argued* to see through *Prismatic Wall* depending on various definitions of light, matter, ethereal, etc. However, D&D 5e is not a physics simulator. Neither *explicitly* states they see through 'planes of shimmering light' or w/e, yet they both talk about seeing through all kinds of stuff, so it's basically an argument either way.

Whenever there's an argument about anything in D&D, it comes down to the DM's decision. That's in large part *why* you have a DM (as well as to apply structure and motivation to the story). What a DM decides is reasonable in that situation is up to the DM and their table's expectations, but,

*Should* Vecna be able to see through his Prismatic Wall?
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Yes.

He is Vecna.