(2023-11-10) If you're casting an adventurer card or split card with escape, you choose how you wish to cast it, then pay the appropriate cost (for the Adventure, the creature, or the half of the split card you chose) plus exiling three cards
Then the Reef is a two-drop enchantment that arrives with four polyp counters
Sadly I have yet to locate any codes being sold or given out for these lands

Out Arcane Endeavor Atris, Oracle of Half-Truths Baleful Strix Burnished Hart Cataclysmic Gearhulk Champion of Wits Clay Golem Cloudblazer Component Pouch Curator of Mysteries Dungeon Map Ethereal Valkyrie Extract Brain Fellwar Stone Grave Endeavor Hostage Taker Merfolk Looter Meteor Golem Minimus Containment Noxious Gearhulk Obsessive Stitcher Phantom Steed Phyrexian Delver Propaganda Rod of Absorption Sepulchral Primordial Solemn Simulacrum Soulherder Sunblast Angel Swords to Plowshares Wall of Omens Wayfarer's Bauble Vanish into Memory In Acererak the Archlich Animate Dead Barrowin of Clan Undurr Blood Artist Bloodghast Carrion Feeder Cave of the Frost Dragon Command the Dreadhorde Consecrated Sphinx Counterspell Deadeye Navigator Doom Whisperer Dovin's Veto Dungeon Descent Ebondeath, Dracolich Faithful Mending Frantic Search Gray Merchant of Asphodel Hall of Storm Giants Hive of the Eye Tyrant Jin-Gitaxias, Core Augur Master of Death Nadaar, Selfless Paladin Path of Peril Phyrexian Reclamation Phyrexian Tower Reassembling Skeleton Reveillark Talisman of Dominance Talisman of Hierarchy Teferi, Master of Time Triumphant Adventurer Viscera Seer

I believe the average 8%-12% fixing density that can be observed on Cube Cobra at time of publishing is a result of many years of inherited rules-of-thumb, unsubstantiated by theory, that can ultimately be traced back to a cards-first, power-driven cube design ethos patterned from retail Limited formats
Soulblade Djinn Casting a steady stream of non-creature spells can turn into a win condition when Soulblade Djinn is on the battlefield