22 cards where the mana value = 6 and the colors is B and the card is tagged “boardwipe”

Ascendant Evincar (Planechase #17)
Blood on the Snow (Kaldheim #79)
Choice of Damnations (Saviors of Kamigawa #62)
Cloudkill (Commander Legends: Battle for Baldur's Gate #121)
Deadly Tempest (Commander 2021 #140)
Demon of Dark Schemes (Kaladesh #73)
Extinguish All Hope (Commander Masters #157)
Feast of Succession (Commander Masters #158)
Final Act (Modern Horizons 3 Commander #52)
Genesis of the Daleks (Doctor Who #69)
Hythonia the Cruel (Theros #91)
Invasion of Fiora // Marchesa, Resolute Monarch (March of the Machine #114)
Invasion of Fiora // Marchesa, Resolute Monarch (March of the Machine #114)
Life's Finale (New Phyrexia #65)
Liliana, Dreadhorde General (Ravnica Remastered #80)
Massacre Wurm (Murders at Karlov Manor Commander #130)
Perforator Crocodile (Alchemy: Murders at Karlov Manor #11)
Rain of Daggers (Masters Edition IV #94)
Sunimret (Mystery Booster Playtest Cards 2021 #47)
Tegwyll's Scouring (Wilds of Eldraine Commander #16)
Their Name Is Death (Warhammer 40,000 Commander #62)
Tsabo's Decree (Invasion #129)
Zombie Apocalypse (Midnight Hunt Commander #131)

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