Activate Bogbrew Witch by paying {2} and tapping it, searching your library for Festering Newt and putting it onto the battlefield.
Activate Ashnod's Altar by sacrificing Festering Newt, adding {C}{C}.
When Festering Newt dies, it, Bogbrew Witch and Mortuary trigger.
Resolve the Festering Newt trigger, giving any creature an opponent controls -4/-4 until end of turn.
Resolve the Mortuary trigger, putting Festering Newt on top of your library from your graveyard.
Resolve the Bogbrew Witch trigger, untapping it.
Repeat.

Infinite death triggers

Infinite creature ETB

Infinite creature LTB

Infinite creature sacrifice triggers

Reduce the toughness of creatures opponents control to 0

Bogbrew Witch

Festering Newt

Mortuary

Ashnod's Altar

Thornbite Staff

Activate Bogbrew Witch by paying {2} and tapping it, searching your library for Festering Newt and putting it onto the battlefield.
When Festering Newt enters the battlefield, Intruder Alarm triggers, untapping all creatures.
Activate Ashnod's Altar by sacrificing Festering Newt, adding {C}{C}.
When Festering Newt dies, it and Mortuary trigger.
Resolve the Festering Newt trigger, giving any creature an opponent controls -4/-4 until end of turn.
Resolve the Mortuary trigger, putting Festering Newt on top of your library from your graveyard.
Repeat.

Infinite mana creatures you control can produce

Infinite untap of creatures

Intruder Alarm

Activate Bogbrew Witch by paying {2} and tapping it, searching your library for Festering Newt and putting it onto the battlefield.
When Festering Newt enters the battlefield, Intruder Alarm triggers, untapping all creatures.
Activate Ashnod's Altar by sacrificing Festering Newt, adding {C}{C}.
Festering Newt is put on the bottom of your library instead of your graveyard due to Wheel of Sun and Moon.
Repeat.

Wheel of Sun and Moon

Combos with "Festering Newt"