Having the Necrotic Ooze in play and Triskelion and Phyrexian Devourer in your graveyard, you essentially give both creature’s abilities to the Ooze. The first combo I'll introduce is quite famouse. The Main combo line requires Skirge Familiar to be revived with Dread Return so it's hard to avoid being graveyard dependent. In fact it was a very popular combo run in format Legacy. The combo consists of three cards: Necrotic Ooze, Triskelion and Phyrexian Devourer. The key point of this combo is use some way to put Triskelion and Phyrexian Devourer into the graveyard, and then put Necrotic… I think Mikaeus, the Unhallowed + Triskelion is the most resilient of the combos since multiple cards can execute the combo in case you get countered (Ever After , Living Death , … Triskelion & Phyrexian Devourer + Necrotic Ooze; Laboratory Maniac + Hermit Druid or Thought Lash or Tainted Pact or Leveler; I have the deck organized into 7 main categories: Tutor - For queuing up the combo; highest priority, but may have too many in this category as-is.