What would a Warlock understand from written spells outside of their class, via Eyes of the Rune Keeper?

Question

This related question asks if you could transcribe a ritual spell to the warlock book via the Book of Ancient Secrets invocation regardless of spell lists, and the answers were generally "yes, but you can't tell what the spell is".

This other one asks if you had the Eyes of the Rune Keeper invocation, "could you cast a scroll of a spell outside of your spell list?", and the answer, using a quote from Crawford, was that you cannot cast the spell since it was out of your spell list (but it did not state if you could actually read the scroll).

By this point, you can probably guess where I'm getting at.

The description of the Warlock eldritch invocation, Eyes of the Rune Keeper:

You can read all writing. You can comprehend any written word or symbol, should it hold any linguistic meaning.

The rules on scrolls outside of your spell list:

If the spell is on your class’s spell list, you can read the scroll and cast its spell without providing any material Components. Otherwise, the scroll is unintelligible.

Can I understand magical literature that is normally outside of my class list if I have the Eyes of the Rune Keeper?

What would I be able to identify from a written spell with Eyes of the Rune Keeper?

Note: I am not asking if I can cast spells outside of my class with the invocation; I am asking if I can understand the nature of the scroll/spell, even if I can't cast from it.

Related: Can Warlock's Eyes of the Rune Keeper decipher written code?

Answer 1

No. Eyes of the Rune Keeper Does Not Read Spells.

tl;dr "Generally, you would not know anything about a scroll, even if you can read every language. Scrolls don't use a language." – Daniel Zastoupil

In short, the words (if any) could be understood in a literal sense, but that doesn't get the meaning nor substance of the spell. Spells, such as those on scrolls, don't have linguistic meaning. They are a cipher.

A spell scroll bears the words of a single spell, written in a mystical cipher.

Ciphers are (generally) not pronounceable.

An example simple cipher using rot-13 of "i am a cipher" has the cipher text:

v nz n pvcure

There is no meaningful pronunciation once the letters are rotated. Other ciphers such as digraph substitution are even less intelligible.

No Linguistic Meaning.

In the case a cipher is chosen such that the cipher text is pronounceable, they wouldn't necessarily be words with a linguistic meaning. For example, while pronounceable, the following cipher text is gibberish:

malveS IBEr OLma ScriANg BOAGern EYmpGREn ToR nUmialaM

Pronounceable Codes are Cryptolects

While the warlock would be able to technically read and pronounce the words, they would be unintelligible.

The ability does not now endow the possessor with the ability to understand codes. Even if the spell was not strictly a cipher, but a cryptolect analogous to thieve's cant or irish traveller's language, it would still be unintelligible.

As Crawford says in this tweet:

Eyes of the Rune Keeper lets you read all writing. That doesn't mean you understand a secret code being delivered by that writing. For example, you might read, "Sunset Dog Potato," and have no idea that's code for something. #DnD

Reading & Casting Clarification by JC

Jeremy Crawford answered a related question about casting in this thread.

JC: Eyes of the Rune Keeper lets you read any form of writing, including the linguistic meaning of a rune, if any. #DnD

@ZerounTheQuick: So does that mean they could read spell scrolls and cast with the normal DC for spell scroll castings?!

JC: Nope.

Answer 2

The ability states that "You can comprehend any written word or symbol, should it hold any linguistic meaning." The magical properties of a spell scroll have nothing to do with its linguistic meaning, so simply being able to read the words on the scroll does not allow you to bypass class requirements for casting spells and the like. You could probably still read the literal words on a spell scroll, you just won't know how to use them to cast the spell. And of course, this is all assuming that the scroll is even written using words with linguistic meanings, which is not necessarily the case.