The core rule books says: "You are a blood descendant of (...) or a supernatural being (such as a dragon)."
How are you managing that in your Saga?
It seems that either one of the parents is of Mythic Blood too, or one of the parents is a supernatural being.
The first case is likely to be the most common, but it can exist only if the second case happened.
Did you design characters that are direct descendants of a supernatural being?
In the case of my character, my current idea is to have him being the son of Great Beast, a pre-hermetic shapeshifter that transformed into a griffin after his Final Twilight, and that transforms back to a memoryless human one night every seventy-seven years. This is a way to explain why my character has the lycanthropy flaw, and why his supernatural parent abandoned him.
Yes, of course, it is possible that the parent who is descendant of a supernatural being does not manifest the Mythic Blood virtue.
But my question was about the case where one of the parents is a supernatural being.
Dragons are known to be able to transform into humans, so it is not really an issue, but Great Beasts are not supposed to transform to humans anymore, therefore it is not easy to find how one can be the direct progeny of a Great Beast.
Looking at HoH:MC, page 37 says "Gifted children may arise from the interaction of the Great Beasts with shapechanged humans" but page 18 mentions that "a child with an animal father appears to lack a soul (the normal state for mundane animals), and always has the mind of a beast (that is, possesses Cunning rather than Intelligence). Children with animal mothers are always born as animals, and appear to be no different from mundane beasts". It would seem that interactions of Great Beasts with shapechanged humans result in soulless creatures.
I have found a partial solution in HoH:MC page 29: " Great Beasts (...) were once human, and most are still in possession of true Intelligence". It suggests that the child of a Great Beast and a shapechanged human has Intelligence. However, there are still a few issues:
this child would be born in animal form, and I don't know the rationale for this child to be able to shapechange to human form as a baby
some Great Beasts are much larger than shapechanged humans (examples from the book are Griffin or Phoenix)
Other question... the core rulebook says "Mythic Blood is not particularly uncommon in the Order of Hermes", but how does one detect that someone has Mythic Blood? Is there some Intellego spell that look for a mythic ancestor (wizard of legend or supernatural creature) or is it just the potent Gift that prevents losing Fatigue when casting higher level formulaic spells?
I would vote for the first option, but a generic spell might not be sufficient to get more information than "has Mythic Blood", and one would need to invent a spell dedicated to one target magi to learn about his/her ancestors. I have not seen such a spell in the books.
I wouldn't get too much into how such a Magi has come about. It shouldn't even be a part of the game, in my opinion, but just a background piece of information. This should be especially true for Great Beasts, who might have strange powers.
As for how to detect it, this is one of those things that if a Magi's Gift is Opened, would just manifest on its own while he was an apprentice, in my opinion. Or, if you want, you could use the InCo Guideline 5: Sense a specific piece of information about a body. And I'd require a Vim requisite to detect Mythic Blood.
Maybe take a cue from the discussion of Faerie Blood in RoP: Faerie, where someone with faerie blood is not necessarily the child (or other descendant) of a Faerie. In particular, Padfoot Blood can occur to the offspring of a pregnant woman who was protected by the Padfoot -- the child can bear animal features from that interaction alone.
Someone with Mythic Blood from a Great Beast maybe just had a significant interaction with the Great Beast.
Interesting... because the core rulebook says for Faerie Blood "Somewhere in your ancestry there is a faerie", but indeed RoP:Faerie does not restrict it to ancestry: "Whenever a faerie derives vitality from a human, the resultant glamour has the power to create a child with faerie blood, the most common method being procreation" and later on "Faerie Blood can be induced without ancestry".
But I'd say that the same rules apply to Magical Blood from RoP:Magic, and that Mythic Blood might be different.
Hmm. When the options for your supernatural parent include demons, angels, and ghosts, it seems rather quaint to go with a Real Big Raccoon. But if it works in your saga, go for it.
Possibly. Castor and Pollux - one had Zeus blood.
Merovech's pregnant mother had an encounter with a Quinotaur.
Siegfried drank the blood of a dragon and learned the languages of the birds. What would his descendents get?
In the Transylvanian book there are Hedge Wizards who eat the Heart of a Giant and gain the Giant Blood virtue.
There is precedent in ME that what us moderns call direct ancestry is not quite the same as Mythic ancestry, and the way to get various mystical blood.
Conceivably this includes Mythic Blood.
Also keep in mind RoP:Faerie in their descriptions of how faerie blood can be acquired after birth, I would assume the same can be true of mythic blood. The most common example from myth being eating the heart or drinking the blood of a dragon.
I love the idea of your character being the son of a Great Beast—definitely adds a lot of depth! For my character, I went with the idea of a distant ancestor who was an elemental. It gives them a connection to the supernatural without going overboard with direct bloodlines, and it keeps their story grounded in humanity. I like how it allows for some mythic traits to show through but still leaves room for character growth and flaws, without feeling like their powers are the main focus. It’s fun finding that balance between the mystical and the personal side of a character.
Nice suggestion, I didn't look at InCo, I was focused on InVi.
That's a rather low base level, it is coherent with the fact that characters know that they have mythic blood: a level 5 spell can be cast spontaneously on self, even with zero in all the three arts.
I suppose that InCo(Vi)5 would only detect that one has Mythic Blood, and InCo(Vi)10 would be needed to know the type of mythic ancestor (a Griffin in my case).
I think a Magus with Mythic Blood would know about the ancestor. Your own parens would have looked into what kind of Mythic Blood you have when it manifested, if only to know what they're dealing with.
This is an hermetic virtue that is IMHO a very good candidate for being the consequence of some original research in the early times of the Order of Hermes.
Here is a proposed story: one of Bonisagus apprentices found an apprentice that had a mythic ancestor, resulting in on virtue (the Special Magic Feat) and one flaw (the Minor Personality Flaw). His original research resulted in a Major Breakthrough that created a new Hermetic Virtue, allowing the magi that have a mythic ancestor to have a Minor Magical Focus related to this ancestor, and the capability to benefit from their strong blood to cast formulaic spells at -10 without spending fatigue. As Mythic Blood is not particularly uncommon, this knowledge has been included in the basic teachings of hermetic theory and can be used by anyone opening the arts of his/her apprentice.