When you cast this spell, reveal cards from the top of your library until you reveal X creature cards. Put all creature cards revealed this way into your graveyard, then put the rest on the bottom of your library in a random order.
Old Stickfingers's power and toughness are each equal to the number of creature cards in your graveyard.
Cast Old Stickfingers for a large X to dump a pile of creatures into your graveyard, then reanimate the best ones and grind value while Stickfingers itself becomes a huge, cheap beater. You self-mill, recur threats, and convert that graveyard mass into either combat damage or an aristocrats/combo finish.
Acts as both a mass self-mill engine and a free, scalable body for reanimator decks
Cheap commander cost means you can recast it and re-mill if it dies
Golgari has the best graveyard recursion and sacrifice tools in the format
Can pivot between voltron beatdown, aristocrats, and reanimator combo
Casting for high X exiles your library randomly to the bottom, risking lost key spells