Say I’m a Pact of the Tome warlock with the Book of Ancient Secrets invocation. I have Detect Magic in my Book of Shadows as a ritual spell. I otherwise don’t know Detect Magic.
Can I make a scroll of Detect Magic?
I’m pretty sure the answer is no, since a ritual spell in my book doesn’t count as a spell known, but it feels a little strange since I can cast the spell as much as I want (albeit as a ritual).
Best Answer
No, they can't; only known spells can be scribed into scrolls.
The optional rules on scribing a spell scroll state (Xanathar's Guide to Everything, p. 133; emphasis mine):
The Book of Ancient Secrets eldritch invocation states:
Nothing in the description of the invocation says that you know the spell, and it actually says such spells don't count against the number of spells you know. It also specifies that you can't cast them except as rituals unless you learn them in some other way (i.e. you can't cast them as regular warlock spells if you haven't learned them as a warlock specifically). Thus, since they're not added to your regular known spells, you can't craft spell scrolls of them either.