Kozilek, the Great Distortion is kinda fun if you can get it into play and have a way to draw cards at instant speed (like Geier Reach Sanitarium), and have enough dredge options in your grave already. I think Sidisi might be the quicker option, while Muldrotha will let you build a stronger board state, but tie up mana resources in the process, slowing down the dredge engine. I consider Sidisi, Brood Tyrant and Muldrotha, the Gravetide to be interchangeable commander options, as the deck isn't likely to be built around either one more than the other.

Just depends on if you run your deck lean/rich on normal card draw.) (Discard/draw options are preferred over draw/discard if you regularly find yourself with no cards left but if you draw a lot of extra cards and keep a rather full hand, then lean on draw/discard options. You can't have enough discard/draw options in here! It would be interesting to streamline the deck down to dredge cards, lands, discard/draw cards, and the three wincons above. And it should be realized that instant spells and tap abilities that force a player to discard and draw can 1) win you the game once your library is empty, 2) force someone to lose (at instant speed, which can be useful) if their library is found to be empty, or 3) fuel the engine of dredge cards being discarded and dredge-drawn, self-milling yourself. Recursion abounds to get those back in hand/play if needed. That of course relies on Laboratory Maniac, Jace, Wielder of Mysteries, and Thassa's Oracle to try and get the wincon. With creatures that tap to do this, and instants that do the same, with a priority on choosing any player (in case we can mill one to death), it's an on-demand game-changer under the right conditions. simply discard dredge cards in exchange for your dredged back cards, milling yourself as the consequence. This is a dredge-engined deck fueled by draw/discard or discard/draw mechanics, letting you keep reusing the best dredge cards to mill yourself every time you discard/draw.

Sidisi budget dredge