18 cards where the cards aren’t reprints and the mana cost is greater than or equal to {8}{G}

Ghalta, Primal Hunger (Rivals of Ixalan #130)
Apex Devastator (Commander Legends #217)
Earthquake Dragon (Commander Legends: Battle for Baldur's Gate #228)
Worldspine Wurm (Return to Ravnica #140)
Nyxborn Behemoth (Commander Masters #742)
Primeval Protector (Commander 2016 #23)
Primal Surge (Avacyn Restored #189)
Thrasta, Tempest's Roar (Modern Horizons 2 #178)
The Pride of Hull Clade (Murders at Karlov Manor #172)
Hierophant Bio-Titan (Warhammer 40,000 Commander #92)
Rumbleweed (Outlaws of Thunder Junction Commander #32)
Lumbering Megasloth (Fallout #80)
Vitalizing Wind (Prophecy #133)
Autochthon Wurm (Ravnica: City of Guilds #191)
Iname as One (Saviors of Kamigawa #151)
Feral Incarnation (Magic 2015 #174)
A-Earthquake Dragon (Alchemy Horizons: Baldur's Gate #A-209)
Who // What // When // Where // Why (Unhinged #120)

Though this query has ended, its relics still slumber in New Argive.