If I control a Thalia, Guardian of Thraben, and an opponent casts Bloodbraid Elf with no untapped sources of mana except Deathrite Shaman (there is a land in a graveyard), cascading into a noncreature spell, can they cast it?
More specifically, is there an opportunity after the cascade trigger begins resolving in which you can activate abilities for mana that are not mana abilities in order to pay the additional cost?
No, there is not. You cast the revealed spell while the cascade trigger is resolving. Since the Shaman does not have a mana ability (since it targets, that makes it not a mana ability), you cannot activate it while the cascade trigger is resolving.
DCI Level 2 Judge

Diego C ha scritto:
"Un cuba libre" "Troppo ghiaccio, mulligo"
ziovec ha scritto:
A noi piacciono le brainstorm
Der_Wolf ha scritto:
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