Teferi, Mage of Zhalfir I like to think about Teferi, Mage of Zhalfir as Michael Jordan, as it can basically do everything despite being a simple creature
Not great but lifegain is a good counter to burn decks
Digging until you hit a shrine allows you to build Hei Bai with a light flicker sub theme
Underworld Breach and Thassa's Oracle are heavily-played combo pieces, while Uro, Titan of Nature's Wrath is a frequent flier on ban lists
Ive heard comments that the deck is too tight of a package to really evolve much, but I hope this has given you some idea of how many different ways there are to approach these kinds of synergies, where this deck can safely be tweaked, and whats really important
And at its worst, Shredders Technique is extra redundancy for a black deck that otherwise couldnt hit enchantments