Polukranos and Genesis Hydra, and even Whisperwood Elemental had the ability to take games over by themselves, even though they could be deployed earlier than when you would normally consider a payoff card entering the battlefield
However, it has held up considerably better in value since its release
Do you have a way to represent copy tokens clearly
First up, lets take a look at some of the spells that can be cast from other zones
The original mutate cost of this card is on the expensive side, but when another creature like Migratory Greathorn is mutated onto it afterwards for cheap, you can repeat the damage and lifegain multiple times
4 Rusko, Clockmaker Life Drain With Extra Mana And Blink Synergy Rusko, Clockmaker seems like a weak card in terms of mana costs and abilities, but is surprisingly reliable and can be used to completely control the game soon after it lands on the battlefield