Fast mana into tutors: Sol Ring, Dark Ritual, and Arcane Signet deploy early acceleration. Demonic Tutor and Diabolic Intent, plus 2 more tutors find your combo pieces or the tutors themselves—Demonic Tutor and Diabolic Intent are unrestricted searches, while Entomb puts a piece directly into your graveyard (fueling Gravecrawler's recursion) and Profane Tutor suspends for free mana value. Buried Alive fetches up to three creatures at once, letting you assemble Gravecrawler, Pitiless Plunderer, and a third piece in one spell. The Demonic Consultation kill: Cast Demonic Consultation for one black mana, name Thassa's Oracle (which you do not have in your library), exile your entire deck, then cast Thassa's Oracle for two blue mana. Oracle enters, checks your devotion to blue (the number of blue mana symbols in your permanents' costs), and if that number is greater than or equal to the cards left in your library (zero), you win immediately. The Gravecrawler loop: Sacrifice Gravecrawler to Ashnod's Altar for two colorless mana. Pitiless Plunderer triggers, creating a Treasure token. Tap and sacrifice the Treasure for one black mana. Cast Gravecrawler from your graveyard for one black mana. Repeat infinitely, generating infinite mana, infinite death triggers, and infinite Slug tokens from Toxrill if it's in play. This loop kills via Gray Merchant of Asphodel (each opponent loses life equal to your black devotion) or by draining with Toxic Deluge (pay life to deal that much damage to all creatures). The Toxrill lock: Toxrill enters and begins putting slime counters on opposing creatures each end step. The Toxrill, the Corrosive + Maha, Its Feathers Night loop produces Reduce the toughness of creatures opponents control to 0 on each of your turns on its own — it needs a separate finisher to actually win. This lock requires no further action—it simply wins over time. Card selection and protection: Cheap cantrips (Ponder and Preordain, plus 3 more card-draw pieces) and card-draw spells (Mystic Remora, Mind Stone, Skullclamp) keep your hand full and dig toward combo pieces. Counterspells (Counterspell and Pact of Negation, plus 2 more counterspells) protect your combo turn or the pieces themselves. Muddle the Mixture is load-bearing: it counters noncreature spells and transmutes for two blue mana to find any two-mana instant or sorcery, including Demonic Consultation or Thassa's Oracle if you need them mid-combo.
The Gravecrawler + Pitiless Plunderer + Ashnod's Altar loop produces Infinite colorless mana, Infinite death triggers, Infinite ETB, Infinite LTB on its own — it needs a separate finisher to actually win. Toxrill, the Corrosive serves as a secondary lock: each end step it puts slime counters on opposing creatures, reducing their toughness by 1 per counter, and when paired with Maha, Its Feathers Night (which sets all opposing creatures to base 0 toughness), those creatures die automatically each turn. The deck wins by assembling one of these three lines as fast as possible, protected by cheap interaction.