Yawgmoth, Thran Physician turns expendable creatures into cards and control over creature size. Paying one life and sacrificing another creature lets you draw a card and optionally place a -1/-1 counter on a target creature. Because targeting is optional, you can use the draw engine even when there is no creature you want to shrink, provided you can pay the life and sacrifice costs.
Token makers such as Ophiomancer supply repeatable material, while Blood Artist or Zulaport Cutthroat can help offset the life payments and pressure opponents. Undying creatures such as Geralf's Messenger add another layer: removing their +1/+1 counters through opposing -1/-1 counters can make future undying triggers possible. The exact loop depends on the other creatures, life total, and payoffs available.
Yawgmoth also lets you pay two black mana and discard a card to proliferate. That can increase existing -1/-1 counters on opposing creatures or advance counters on your own permanents. Proliferate only adds kinds of counters already present, so it cannot create the first counter on an object that has none.
Protection from Humans gives him a useful defensive edge, but the engine still needs creatures and life to operate. Build with a healthy supply of bodies and ways to recover resources rather than assuming the commander alone provides everything. The strongest turns turn creatures you were willing to lose into both a larger hand and a less threatening opposing board.
