For value, OP-11: A Fist of Divine Speed offers the best risk-to-reward ratio at near-MSRP pricing with high-ceiling chase cards
Inventor's Fair), help with improvise (e.g
Grixis Shadow 4 Deaths Shadow 4 Gurmag Angler 4 Scourge of the Skyclaves 4 Street Wraith 1 Agadeems Awakening 2 Dismember 2 Fatal Push 2 Inquisition of Kozilek 4 Lightning Bolt 4 Mishras Bauble 3 Stubborn Denial 2 Temur Battle Rage 4 Thought Scour 4 Thoughtseize 2 Blood Crypt 2 Bloodstained Mire 1 Snow-Covered Island 4 Polluted Delta 3 Scalding Tarn 1 Steam Vents 1 Snow-Covered Swamp 2 Watery Grave SIDEBOARD 1 Stubborn Denial 2 Kolaghans Command 1 Go for the Throat 1 Fatal Push 2 Aether Gust 2 Collective Brutality 2 Nihil Spellbomb 1 Plague Engineer 1 Snapcaster Mage 1 Mystical Dispute 1 Ceremonious Rejection Historically, one of the weaknesses of Grixis Deaths Shadow has been threat density
Perhaps that common is a powerful card in its own right, like Lightning Bolt
A Texas man could be in line for a significant windfall after stumbling on a pristine condition Pokmon card he stowed away inside a book 20 years ago
Its also worth noting that you get diminishing returns for Mutating multiple timesthe first Mutation likely involves a hefty upgrade to a creatures stats, while subsequent ones are probably defined more by getting value from multiple when-this-Mutates abilities