Casting spells using the Book of Ancient Secrets

I am playing a 3/3 Divine Soul Sorcerer/HexBlade Warlock, and have just chosen the Pact of the Tome, along with the Book of Ancient Secrets.

I have found a spellbook with Identify, which I am now transcribing into the book. I also have Unseen Servant as a known spell. I create a scroll, using the Arcana skill. And then use the scroll to transcribe the Unseen Servant spell to the Book. The Scroll is destroyed in the process. So far, so good.

I then replace Unseen Servant with Charm Person on my list of known spells.

Can I still cast the Unseen Servant as a ritual from the book?

Can I cast the Unseen Servant as a spell, using the book and a spell slot? This question arises from the interpretation from the text “You can’t cast the spells except as rituals, unless you’ve learned them by some other means.

If this is possible, it basically means I have an external memory extension, that when held, allows me access to cast any of the entries as a ritual.

And cast the spells that previously were known spells from my spell list that has been transcribed into the book, as spells, using spell slots.

How do Eberron Dragonmarks and Book of Ancient Secrets Invocation interact?

I might be over-analyzing and confusing myself, but I’m not certain regarding the interaction between Dragonmark learned Ritual spells and the Book of Ancient Secrets warlock invocation.

Let’s take as an example the Mark of Hospitality subrace’s trait:

Spells of the Mark. If you have the Spellcasting or the Pact Magic class feature, the spells on the Mark of Hospitality Spells table are added to the spell list of your spellcasting class.

This list includes ritual spells like, Leomund’s tiny hut, Mordenkainen’s private sactum and hallow.

Now let’s take the Book of Ancient Secrets invocation:

You can now inscribe magical rituals in your Book of Shadows.[…] You can also cast a warlock spell you know as a ritual if it has the ritual tag.

On your adventures, you can add other ritual spells to your Book of Shadows. When you find such a spell, you can add it to the book if the spell’s level is equal to or less than half your warlock level (rounded up) and if you can spare the time to transcribe the spell. For each level of the spell, the transcription process takes 2 hours and costs 50 gp for the inks needed to inscribe it.

In order to ritual-cast these spells (added to my list by the Dragonmark) as non-prepared spells, but rather as ritual spells from my Book of Shadows, which of the following mechanism is appropriate, per RAW (and/or RAI):

  1. Do they count as warlock spells (by being added to my spell list as per the spells of the mark trait), thus I can cast them without preparation since they have the ritual tag (as per the Book of Ancient Secrets Invocation?)
  2. Do I magically learn them (as per the spells of the mark trait) but I have to spent time to transcribe the spell in the Book of Shadows, although I don’t have a physical written form of the spell?
  3. It does not satisfy either mechanism, and the only way to cast these spells is to prepare them as warlock spells, until I find them in written form and can transcribe them in the Book of Ancient Secrets?

Should I have to roll to copy a spell into my Book of Ancient Secrets?

The Book of Ancient Secrets invocation says (PH p. 110):

On your adventures, you can add other ritual spells to your Book of Shadows. When you find such a spell, you can add it to the book if the spell’s level is equal to or less than half your warlock level (rounded up) and if you can spare the time to transcribe the spell. For each level of the spell, the transcription process takes 2 hours and costs 50 gp for the rare inks needed to inscribe it.

There’s no mention of rolling anything.

But in the DMG (p. 200) under the Spell Scroll magic item it says:

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.

This entry refers specifically to wizard spells, and seems to be more directed toward wizards copying wizard spells into their spellbooks, but since warlocks can copy any scroll that would also include wizard scrolls.

I’ve copied one spell already in our campaign, and the DM didn’t call for a roll, which is fine with me, but I’m just wondering if anyone knows what was intended.

Can i dimension door ONTO the back of, say, an ancient green dragon?

I am familiar with the DMG rules for climbing on to the back of a larger creature, and I think that dimension door or perhaps misty step would allow me to bypass the Opposed dex vs str/dex check, to place myself onto its back. From there, it can use its action to shake me, or whatever the dm can come up with, mostly im curious about rulings for teleporting ONTO a creature. Certainly the place it is is occupied, but im not trying to land there. What say ye, oh wise masters?

Can I true polymorph into an Ancient Brass Dragon, and then use its Change Shape ability?

If I were to cast True Polymorph (which permits all creatures, not just beasts, as the regular Polymorph does) on myself to turn myself into, say, an Ancient Brass Dragon (provided that I’m level 20, which is required due that dragon’s CR) – could I then use the Change Shape “racial” feature of the dragon?

Change Shape. The dragon magically polymorphs into a humanoid or beast that has a challenge rating no higher than its own, or back into its true form…

True Polymorph:

Choose one creature […] that you can see within range. You transform the creature into a different creature, […]. The transformation lasts for the duration, or until the target drops to 0 hit points or dies. If you concentrate on this spell for the full duration, the transformation becomes permanent.
Shapechangers aren’t affected by this spell. […].

Creature into Creature
[…] The target’s game statistics, including mental ability scores, are replaced by the statistics of the new form. It retains its alignment and personality. […]

I can’t find anything in the spell that would prevent one from doing so. The only thing that might come into play is the phrase “Shapechangers aren’t affected by this spell”. You as the caster are not a shapechanger, however, so even though you transform into a shapechanger, you aren’t when you cast the spell.

How does the Commune spell work when cast by someone with the Ritual Caster feat or a warlock with the Book of Ancient Secrets invocation?

The D&D 5e spell Commune is a Cleric spell that contacts the Cleric’s chosen divine proxy and asks them three ‘yes or no’ questions. It is a ritual spell, so a Warlock with Book of Shadows or anyone with the Ritual Caster feat really can learn and cast the spell.

Let’s say an atheist wizard uses the Ritual Caster feat to learn Commune (gaining Ritual Caster does not require belief in any pantheon) and then casts it (which can be done through an arcane focus). Who would she encounter? (If it helps, the Wizard belongs to the School of Divination.)

If an Ancient Metallic Dragon uses Change Shape to turn into a humanoid with Innate Spellcasting, do the uses of “X/day” spells reset each time?

Ancient Metallic Dragons (e.g. Ancient Brass Dragons) have the Change Shape ability:

Change Shape. The dragon magically polymorphs into a humanoid or beast that has a challenge rating no higher than its own, or back into its true form. It reverts to its true form if it dies. Any equipment it is wearing or carrying is absorbed or borne by the new form (the dragon’s choice).

In a new form, the dragon retains its alignment, hit points, Hit Dice, ability to speak, proficiencies, Legendary Resistance, lair actions, and Intelligence, Wisdom, and Charisma scores, as well as this action. Its statistics and capabilities are otherwise replaced by those of the new form, except any class features or legendary actions of that form.

It is my understanding that the Spellcasting feature is a class feature and thus unavailable to an Ancient Metallic Dragon, but that the Innate Spellcasting trait is available to them.

Now, let’s take in example the Gloom Weaver humanoid from Mordenkainen’s Tome of Foes (p. 224), who has the following not-at-will Innate Spells:

1/day each: arcane gate, bane, compulsion, confusion, true seeing

If, say, an Ancient Brass Dragon decides to use Change Shape to turn into a Gloom Weaver, then decides to cast its 1/day true seeing, then uses Change Shape to revert to their dragon form, and uses it yet again to become a Gloom Weaver once more… does the dragon thus have a new use of true seeing?

In other words, does an ancient metallic dragon have essentially unlimited “X/day” innate spells by way of using Change Shape back and forth?

Does a spellcaster with Lair actions keep them when Shapechanging into an Ancient Metallic Dragon who then uses Change Shape?

A few high level arcane spellcasting monsters, such as the Lich from the Monster Manual, also have Lair Actions.

Such spellcasters can prepare then cast Shapechange on themselves to become an Ancient Metallic Dragon (such as a Brass one), while keeping some things :

You retain the benefit of any features from your class, race or other source and can use them, provided that your new form is physically capable of doing so.

It is my understanding that the above would allow the Lich to keep its Lair actions in dragon form.

Such dragons have a special Change Shape ability to transform into a humanoid or beast (such as a rabbit) while keeping certain things :

[…] retains its alignment, hit points, Hit Dice, ability to speak, proficiencies, Legendary resistances, lair actions, and Intelligence, Wisdom and Charisma scores, as well as this action.

It is clear from the Monster Manual’s Errata that the Lich could not gain the Dragon’s Lair actions (or the resulting beast/humanoid lair actions, if any) :

If a creature assumes the form of a legendary creature, such as through a spell, it doesn’t gain that form’s legendary actions, lair actions, or regional effects.

But what I’m wondering here is whether the now-twice-transformed creature would retain its initial form’s Lair actions. In this example, would the Lich-transformed-into-an-Ancient-Brass-Dragon-transformed-into-a-Rabbit keep its Lich Lair actions ?

Can a Tomelock swap the Book of Ancient Secrets invocation with itself upon level-up, and gain more than two ritual spells that way?

Eldritch Invocations (PHB, p. 107):

…Additionally, when you gain a level in this class, you can choose one of the invocations you know and replace it with another invocation that you could learn at that level.

Book of Ancient Secrets (BoAS) (PHB, p. 110):

Prerequisite: Pact of the Tome

You can now inscribe magical rituals in your Book of Shadows. Choose two 1st-level spells that have the ritual tag from any class’s spell list (the two needn’t be from the same list). The spells appear in the book and don’t count against the number of spells you know. With your Book of Shadows in hand, you can cast the chosen spells as rituals. You can’t cast the spells except as rituals, unless you’ve learned them by some other means. You can also cast a warlock spell you know as a ritual if it has the ritual tag.

On your adventures, you can add other ritual spells to your Book of Shadows. When you find such a spell, you can add it to the book if the spell’s level is equal to or less than half your warlock level (rounded up) and if you can spare the time to transcribe the spell. For each level of the spell, the transcription process takes 2 hours and costs 50 gp for the rare inks needed to inscribe it.

Assuming that the DM rules that the Rituals learned by BoAS don’t vanish upon dismissing (old) BoAS:

Is it possible by RAW to gain two new ritual spells with every warlock level by switching the BoAS invocation with the BoAS invocation upon level-up?

Bonus:

Assuming that the DM rules that the spells learned from BoAS vanish:

Can a warlock copy a spell from his Book of Shadows to his Book of Shadows and preserve the Spells in this way to get more ritual spells by switching BoAS with BoAS on level-up?