Activate Yawgmoth's first ability by paying 1 life and sacrificing Thragtusk.
Thragtusk dies, triggering its second ability and its undying ability.
Resolve the first Thragtusk trigger, creating a 3/3 Beast creature token.
Resolve the second Thragtusk trigger, returning it from your graveyard to the battlefield with a +1/+1 counter on it.
Thragtusk enters the battlefield, causing you to gain five life.
Resolve the Yawgmoth ability from step 1, putting a -1/-1 counter on a creature and causing you to draw a card.
Activate Yawgmoth by paying 1 life and sacrificing the Beast token, putting a -1/-1 counter on Thragtusk and causing you to draw a card.
Repeat.

Infinite card draw

Infinite draw triggers

Near-infinite -1/-1 counters

Near-infinite death triggers

Near-infinite ETB

Near-infinite lifegain

Near-infinite lifegain triggers

Near-infinite LTB

Near-infinite sacrifice triggers

Yawgmoth, Thran Physician

Mikaeus, the Unhallowed

Thragtusk

Activate Emiel by paying {1}, blinking Thragtusk.
Thragtusk enters and leaves the battlefield, triggering its abilities.
Resolve the Thragtusk enters-the-battlefield trigger, causing you to gain five life.
Resolve the Thragtusk leaves-the-battlefield trigger, creating a 3/3 Beast creature token.
Activate Treasonous Ogre by paying three life, adding {R}.
Repeat.

Combos with "Thragtusk"