One of my campaigners and I got into a stupid argument a while back about whether or not a creature with Truesight should be able to bypass the "Wall of Light" spell. This is a homebrew creature (one of two I introduced into the campaign with truesight) that also had blindsight and immunity to the blinded status effects. Lv. 15 campaign- 5e.

For starters, I think whoever wrote the description of "Truesight" in the D&D Beyond glossary either left out information or wasn't given enough to work with. Because according to the glossary, Truesight should only be able to see through magical darkness, illusions (like invisibility spells and other visual illusions), and objects under a transformation. It also allows the creature to see into the ethereal plain.

I ruled as the Dungeon Master in a previous encounter that Truesight shouldn't be able to effect the benefits of 1/2 and 3/4ths cover. I also said that it wouldn't allow the creature to see through walls or other solid objects.

Truesight, at least according to the description of it in the glossary, shouldn't be able to see through spells like "Fog Cloud" because it is not an illusion and not magical darkness. It doesn't make sense that something with Truesight shouldn't also be able to see through those spells effects, however. So to me, Truesight is given to creatures whose sight cannot be limited by magical or environmental effects and cannot be fooled by illusions.

The spell "True Seeing" says that a willing creature you touch gains the ability to "see things as they actually are," and the spell "Wall of Light" says that it "blocks line of sight-" as if it were a solid object.

Both arguments for and against it make sense, but because the Wall of Light spell specifies that creatures and objects can pass through it, I ruled that because the "Wall of Light" wasn't a solid object, the creature would be able to see through it thanks to Truesight and Blindsight.

End of conversation until my campaigner comes back to me the next day saying that what the creature did was impossible and they shouldn't have been able to achieve it. I have nothing against my campaigners, and my goal is not to make their life harder durring combat. But no matter how I sliced it, it didn't make sense that this creature shouldn't be able to see through a wall that doesn't exist. So I stood my ground and explained everything I just laid out here and ended it by saying: "When something like this happens and the rules cannot be discerned because there isn't enough information, it's up to the DMs discretion to decide the answer to what something or someone is capable of doing."

The argument is over now, and we've made up, but I'm curious about your guys' thoughts.

"Wall of Light" Vs Truesight