Ballad of the Black Flag
Enchantment — Saga
(As this Saga enters and after your draw step, add a lore counter. Sacrifice after IV.)
I
, II, III — Mill three cards. You may put a historic card from among them into your hand. (Artifacts, legendaries, and Sagas are historic.)
IV — Historic spells you cast this turn cost 
less to cast.
Miklós Ligeti
Assassin's Creed (ACR)
• #13Rulings
A card, spell, or permanent is historic if it has the legendary supertype, the artifact card type, or the Saga subtype. Having two of those qualities doesn’t make an object more historic than another or provide an additional bonus—an object either is historic or it isn’t.
(wotc • 2024-07-05)
An ability that triggers “whenever you cast a historic spell” doesn’t trigger if a historic card is put onto the battlefield without being cast.
(wotc • 2024-07-05)
Some abilities trigger “whenever you cast a historic spell.” Such an ability resolves before the spell that caused it to trigger. It resolves even if that spell is countered.
(wotc • 2024-07-05)
Lands are never cast, so abilities that trigger “whenever you cast a historic spell” won’t trigger if you play a legendary land. They also won’t trigger if a card on the battlefield transforms into a card with the legendary supertype, the artifact card type, or the Saga subtype.
(wotc • 2024-07-05)
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Rulings
A card, spell, or permanent is historic if it has the legendary supertype, the artifact card type, or the Saga subtype. Having two of those qualities doesn’t make an object more historic than another or provide an additional bonus—an object either is historic or it isn’t.
(wotc • 2024-07-05)
An ability that triggers “whenever you cast a historic spell” doesn’t trigger if a historic card is put onto the battlefield without being cast.
(wotc • 2024-07-05)
Some abilities trigger “whenever you cast a historic spell.” Such an ability resolves before the spell that caused it to trigger. It resolves even if that spell is countered.
(wotc • 2024-07-05)
Lands are never cast, so abilities that trigger “whenever you cast a historic spell” won’t trigger if you play a legendary land. They also won’t trigger if a card on the battlefield transforms into a card with the legendary supertype, the artifact card type, or the Saga subtype.
(wotc • 2024-07-05)