As a longtime Soulflayer fan, I havent ever had the motivation to jump through the hoops to make it or similar cards work in Cube, and Indominus Rex is just easy mode in terms of offering that sort of play experience
1 owyn, Shieldmaiden 1 Aragorn, King of Gondor 1 Beregond of the Guard 1 Champions of Minas Tirith 1 Gilraen, Dnedain Protector 1 Grey Host Reinforcements 1 Lossarnach Captain 1 Archivist of Gondor 1 Denethor, Stone Seer 1 Fealty to the Realm 1 Call for Aid 1 Gimli of the Glittering Caves 1 Boromir, Gondor's Hope 1 omer, King of Rohan 1 Faramir, Steward of Gondor 1 Forth Eorlingas
And we know that 20% of Play Boosters will have a card from The List that's to say, nearly 13 cards among those 64 Play Boosters will be from The List
This ability can be really powerful, potentially allowing Rex to both remove combo pieces from the game and provide you access to combo pieces from your opponents' and your own deck
If you pay, untap all creatures you control, and after this phase, there is an additional combat phase