Coram, the Undertaker

Most graveyard commanders treat the yard as a resource to reload from; this one treats every library on the table as shared fuel and every combat step as a strip-mining operation. The attack trigger mills all players, so it fills graveyards it fully intends to plunder, and the third ability is the payoff: on your turn you may play a land and cast a spell from among cards that hit any graveyard from a library that turn. That "from libraries this turn" clause is the load-bearing restriction. It excludes the fodder you sacrificed and the creatures that died in combat: only cards that came from a library this turn count, which turns the deck from a reanimator pile into a self-milling engine that has to keep churning to find something worth casting. And the cast is not free; you still pay the spell's mana cost, so what you actually gain is access, not a discount. The 0/5 body is the honest part of the bargain. It attacks for nothing on its own and leans entirely on the +X/+0 pulled from the biggest creature in any graveyard, so the more everyone mills, the harder it swings, and the loop feeds itself: bigger yards, bigger Coram, more mill, a wider pool to reach into. The design fuses two archetypes that usually sit apart, group-slug mill and stolen-tempo value, into a single Jund shell where the two halves are the same action. The trigger that shrinks their decks is the trigger that stocks your options.