A quote from the DMG l found on reddit while researching this topic: A wizard spell on a spell scroll can be copied just as spells in spellbooks can be copied. When a spell is copied from a spell scroll, the copier must succeed on an Intelligence (Arcana) check with a DC equal to 10 + the spell's level. If the check succeeds, the spell is successfully copied. Whether the check succeeds or fails, the spell scroll is destroyed.

But WHY? Why does attempting to copy the spell from a scroll Destroy it? I don't understand. What Lore reason is there for this? It seems kinda silly to have have the scroll self destruct if the copy fails. Like, how does the scroll know it's being copied, or when the copier is finished?

(And please don't say "Magic", that would imply the scroll has some extra form of magic designed specifically to screw wizards over, and l don't see how that could be applied to every spell on their spell list. Actually, knowing wizards, that might be exactly what happens, with the wizard scribing the spell adding minor divination and evocation runes to let it be able to self destruct a set time after it senses someone try to copy it? Either that, or the settings Magic Deity has something to do with it. But this is just me spit-balling, please, if there is a actual answer, please write it below.)

(Also,  someone wants to explain the Out of universe reason for this rule, that would be appreciated, and so l created this thread.)

Edit: @EricHVela Good point. To be clear, when i said "Please don't say Magic" I meant "Please don't make your entire explanation "It's magic, lol". That much is obvious. I Want to know exactly what in world magical phenomena is responsible, or if there even is one, so l can know if I need to house rule it or not.

Spell scrolls are single-use items.  You only get one attempt with one, whether you're trying to cast it or trying to copy it if you're a wizard.  That's really as far as the justification has ever gone.  Scrolls are, after all, fairly fragile things so it's probably based on the idea that they're just not durable enough for multiple uses.  The scroll itself is charged with magic, which gets activated when you try to use the scroll.

This is still not as bad as some older editions.  At one point, wizards did not automatically learn spells upon leveling up, you had to find or buy scrolls for all new spells you wanted to learn.  On top of that, it was a flat percentage chance based on your intelligence score that you'd succeed in copying it to your spellbook, and your intelligence score also dictated how many spells you could copy into it.

You don't want people to say "magic" when describing magic?

You'll never get an answer to which you'd agree, then.

There's no ill intent with scrolls. It's just a limitation of magic. (See? You can't get away from using that word.) The magical (there it is again) energies are imbued into the scroll.

Scrolls are made to contain not only the spell incantation but also energy to cast it. My interpretation of the destruction is that all the words burn away as the magical (once more, with feeling) energy is released. Transcription is not immune to releasing the energy.

If you want an explanation of magic without magic, you're not going to get it.

EDIT: Why a difficulty check to succeed on copying? You have to keep the energies contained until the copying is done. If you don't, the spell's enegy is released and destroys the scroll.

It’s mostly mechanical; the actual lore “reason” why the spell scroll withers is left open to interpretation.

Zee Bashew had an interesting theory; in that the way Wizards copy / memorize their spells is specific to their own eccentric ways of thinking…basically, their notes may seem like nonsense to another wizard, because they think differently.

So I’d like to think that if a wizard copy’s a spell to a scroll, they are literally embedding a portion of their thoughts or memories into the scroll.

This is a valid reason why a wizard must succeed on an Arcana check in order to copy from a scroll…they are bending their mind to try and interpret another Wizard’s notes / abstract thoughts.

I’d like to think that when the abstract thinking of two wizards collide; the scroll lacks the resiliency of a proper spellbook to survive the process…which would be why it turns to dust afterwards. 

If a scroll is not destroyed after copying, then one scroll becomes two becomes four becomes eight becomes...

Now your limited use resource (spellcasting) has unlimited uses...

Those are mechanic reasons (for that other thread mentioned). ITT, what lore would you write to support it in-world?

EDIT: I'm guessing bonus points for going into details and not just typing, "It's magic."

What I posted in the Rules & Game Mechanics thread:

Quote from Haravikk >>

The way to think of it is that a scroll isn't simply a piece of paper with words on it, there is an actual magical spell bound inside the scroll, along with all of the energy required to cast it; remember, scrolls don't consume a spell slot, the scroll itself is destroyed instead, because the energy has to come from somewhere, and it's presumably bound into the scroll itself.

Because of the way the scroll works, copying it isn't as a simple as writing the words from the scroll onto a page in your spellbook; not least of all because the words on the scroll may not be the same as what you need to write into your spellbook, i.e- the words on a scroll tell you what spell it contains and how to trigger it, it doesn't tell you how to learn the spell, or the intricacies of casting it yourself using your own magical energy. It's like comparing a match-stick (use once to light a fire) to a guide on how to build your own cigarette lighter (reusable fire starter requiring only fuel).

With this in mind, the act of copying is actually a transfer of the spell out of the scroll, and transcribing its details into your spellbook so that you know how to cast it yourself in future. But if you fail, you might only succeed in removing the spell from the scroll, and while holding it in your mind for transcription you lose control before you finish, and the spell is lost.

TL;DR
It's a magical process, therefore the answer is "magic".

The process of transcribing a new spell into your spellbook involves figuring out how the spell works. It isn’t a direct copy, it’s more like figuring out the scroll’s author’s shorthand and then substituting your own when adding the spell to your book. I presume that process is similar enough to casting the spell to consume the scroll. 🤷‍♂️

Quote from EricHVela >>

Those are mechanic reasons (for that other thread mentioned). ITT, what lore would you write to support it in-world?

EDIT: I'm guessing bonus points for going into details and not just typing, "It's magic."

 The mechanical reason suggests a lore reason--wizards don't want their tools used against them. They add a magical clause at the end of every spell copied to a scroll which destroys the scroll after it has been used. Wouldn't want thief rogues casting unlimited use etherealness as a bonus action. That's bad for business...

Quote from eapiv >>

If a scroll is not destroyed after copying, then one scroll becomes two becomes four becomes eight becomes...

Now your limited use resource (spellcasting) has unlimited uses...

 Obviously when it's used to cast the spell, it should be destroyed. My Question was why it's destroyed when you try to copy it, which costs time and gold. Also, RAW, anyone with Arcana Proficiency can create scroll versions of the spells they can cast, as long as they have the time and gold, so having the scroll that you can copy into a spell book (To then cast whenever and create new scrolls)  and also still have to cast, isn't nearly as game breaking as you make it sound.

Quote from IamSposta >>

The process of transcribing a new spell into your spellbook involves figuring out how the spell works. It isn’t a direct copy, it’s more like figuring out the scroll’s author’s shorthand and then substituting your own when adding the spell to your book. I presume that process is similar enough to casting the spell to consume the scroll. 🤷‍♂️

 I Guess that makes sense. Thanks.

When you copy a scroll across to your book, you're not just making the same shapes on a piece of paper - you are moving the spell in the scroll from the parchment it's on now to the paper of the book. You're taking the essence of what the spell is and transferring it, not copying and pasting.

Think of it not as copying the scroll into your book, instead think of it as moving the spell from the scroll and into your book - in the same way a barbarian might move an entire ham from a fire to his stomach, or a rogue might move a coinpurse from a passerby to their pouch. Both of them would be happy if the item was still there afterwards, but it's not!

(Boom, didn't say the "M" word once!)

Quote from ThorukDuckSlayer >>

When you copy a scroll across to your book, you're not just making the same shapes on a piece of paper - you are moving the spell in the scroll from the parchment it's on now to the paper of the book. You're taking the essence of what the spell is and transferring it, not copying and pasting.

Think of it not as copying the scroll into your book, instead think of it as moving the spell from the scroll and into your book - in the same way a barbarian might move an entire ham from a fire to his stomach, or a rogue might move a coinpurse from a passerby to their pouch. Both of them would be happy if the item was still there afterwards, but it's not!

(Boom, didn't say the "M" word once!)

 That actually a very reasonable explanation! Thanks!