Changes:
Gilded Drake -> replace Phantasmal Image
Urza's Saga -> replace Sulfur Falls
Bloodstained Mire -> replace Cascade Bluffs
Cephalid Coliseum -> replace 1 Island
Mana Drain -> replace Counterspell? (Make proxy alter sleeve?)
Timetwister -> replace FLooting?
Mox Opal -> replace City of Brass?
Grim Monolith -> replace Swiftfoot Boots
Bribery -> replace Kazuul's Fury
? -> replace Rapid Hybridization?

Need:
** $$$$$ Lion's Eye Diamond
* $$$$$ Jeweled Lotus
* $$$$$ Mox Diamond
* $$$$ Mox Opal
$$ Cephalid Coliseum

Consider (have):
* Lotus Petal - Might need this as a backup to get enough mana from a Breach+Freeze loop if I didn't have Scoundrel when going off
Dispel, Miscast - Cheap interaction
Unsubstantiate - Venser effect to buy time, or another way to bounce Zndrsplt to avoid decking
Lightning Bolt - Cheap removal
Hydroblast - Counter Pyroblast, Purphoros etc
Thieving Skydiver - Steal a rock
Fiery Gambit - Up to three coin flips with sweet effects, but I probably need some Krark available before I cast it
Rite of Replication - Another card to combo with Dualcaster, and otherwise just good blue stuff
Niv-Mizzet, Parun - Deal some damage when Zndrsplt draws us a bunch of cards
Thassa's Oracle - Draw my deck with Zndrsplt + Efreet then win
The Royal Scions - Can give Okaun trample, or loot away cards, but I can't really protect them if people want to just attack it down
Valakut Awakening - Wheel away the stuff I don't need, or be a land in an emergency
Stitch in Time - Extra turn

Consider (don't have):
* $$$$ Copy Artifact - An extra thumb
$$$$$$ Wheel of Fortune
$$$ Bribery - Steal someone else's Thassa's Oracle when I draw my whole deck, or shuffle titan to enable mill win
Rushing River
$$ Karplusan Minotaur - A lot of flips and potentially removal, but it's risky
$$ Seize the Day - Extra combats
Goblin Archaeologist - Flip a coin and maybe destroy an artifact, for R per attempt until I fail
Chaotic Strike, Aleatory - Cheap cantrips that flip a coin and give a minor buff

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Considered cuts:
Rogue's Passage - Expensive to use, and colorless
Cascade Bluffs - Doesn't tap for mana when it's my only land
Phantasmal Image - Nice to copy a Dockside, but might not have use for other things so this risks being pretty dead
Kazuul's Fury - Unlikely to win with Okaun at a high power level, but being an MDFC is nice
Rapid Hybridization - 3/3s are big, but other things might be bigger
* Faithless Looting - Card disadvantage
Counterspell - Should be Mana Drain
Rapid Hybridization - A 3/3 is quite big
Swiftfoot Boots, Lightning Greaves - Protection is nice, and haste is also sweet, but if they were gonna die, I probably won't even get these on. Boots costs mana to equip, but Greaves won't let me bounce/Fling

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Cuts from high power:
Fling
Krark - Too risky
Squee's Revenge - Not great without at least one Thumb
Chaos Warp - Expensive removal for a high power level, and potentially risky
Chance Encounter - If I win 10 coin flips and don't win, I'm probably not getting to untap with this either
Goblin Engineer - A lot of work to get the thumb when I probably want to win through combo anyway
Whispersilk Cloak - Probably too expensive for this effect, when the shroud for Zndrsplt is more likely to be used than the unblockable for Okaun
Blasphemous Act - This is rarely going to be very cheap at a high power level, and rarely necessary with 13 damage
Slip Through Space - Untapping with Okaun and getting it huge is probably not that likely at this power level. Also not blue, so can't pitch
Trash for Treasure - Don't really need the Thumb
Frostboil Snarl - Might be hard to get this untapped
Buried Ruin - Losing the thumb is less of a drawback than not having blue mana
Wayfarer's Bauble - Expensive ramp
Thought Vessel - Only taps for colorless
Vandalblast - When am I ever overloading this?
Fabricate, Tribute Mage - Getting the Thumb is nice, but not necessary
Back to Basics - I might be so much more mana hungry than the cEDH version that I can't run this