23 cards where the card types include “instant” and the mana value >= 8

Assure // Assemble (Ravnica Remastered #248)
Bedeck // Bedazzle (Ravnica Remastered #244)
Blinkmoth Infusion (Fifth Dawn #25)
Blood for the Blood God! (Warhammer 40,000 Commander #108)
Boulderfall (Theros #115)
Cease // Desist (Murders at Karlov Manor #246)
Chant of Vitu-Ghazi (March of the Machine Commander #177)
Commit // Memory (The Lost Caverns of Ixalan Commander #147)
Decree of Savagery (Forgotten Realms Commander #156)
Dig Through Time (Duskmourn: House of Horror Commander #115)
Explosive Welcome (Strixhaven: School of Mages #100)
Fast // Furious (Modern Horizons 2 #123)
Flotsam // Jetsam (Murders at Karlov Manor #247)
Fuss // Bother (Murders at Karlov Manor #248)
Gallifrey Falls // No More (Doctor Who #131)
Hit // Run (Dissension #152)
Lavaball Trap (Zendikar #135)
Magma Opus (Strixhaven: School of Mages #203)
Searing Wind (Eighth Edition #218)
Spite // Malice (Dominaria Remastered #208)
Spring // Mind (Amonkhet #219)
Vitalizing Wind (Prophecy #133)
Who // What // When // Where // Why (Unsanctioned #75)

Their mind whirled with grand plans, never thinking of what might happen if they got to the end of the list.