Whenever you cast a historic spell, draw a card. (Artifacts, legendaries, and Sagas are historic.)
A spell is historic if it has the legendary supertype, the artifact card type, or the Saga enchantment subtype. Having two of those qualities doesn't make a spell more historic than another or provide an additional bonus—a spell either is historic or it isn't.
An ability that triggers when a player casts a spell resolves before the spell that caused it to trigger. It resolves even if that spell is countered.