Cast Mourning by paying 2 life if able, or {B} otherwise.
Each creature you control's extort ability triggers.
Resolve the first extort trigger, causing you to pay 2 life if able, or {W/B} otherwise, causing each opponent to lose 1 life and you to gain that much life.
Repeat step 3 for each remaining extort trigger.
Resolve Mourning, attaching it to a creature you control.
Activate Mourning by paying 2 life, returning it from the battlefield to your hand.
Repeat until an opponent loses the game due to having 0 or less life.

Near-infinite lifegain

Near-infinite lifeloss

Near-infinite lifegain triggers

Near-infinite storm count

K'rrik, Son of Yawgmoth

Pontiff of Blight

Mourning

Helm of Awakening

Cast Mourning by paying 2 life, targeting K'rrik.
Aetherflux Reservoir and K'rrik trigger.
Resolve the K'rrik trigger, putting a +1/+1 counter on it.
Resolve the Aetherflux Reservoir trigger, causing you to gain an amount of life equal to your storm count.
Resolve Mourning, attaching it to K'rrik.
Activate Mourning by paying 2 life, returning it to your hand from the battlefield.
Repeat.
Once you have infinite life, you may use Aetherflux Reservoir's ability to deal infinite damage to any target(s).

Infinite +1/+1 counters on K'rrik

Infinite damage

Infinite lifegain

Infinite lifegain triggers

Infinite storm count

Aetherflux Reservoir

Cloud Key

Mana Matrix

Activate up to seven lands you control by tapping them, adding at least {1}{B}{B}
Cast Mourning by paying its mana cost, targeting Displacer Kitten
Displacer Kitten triggers, blinking Palinchron.
When Palinchron enters the battlefield, it triggers, untapping up to seven lands.
Resolve the Mourning spell.
Activate Mourning by paying {B}, returning it from the battlefield to your hand.
Repeat.

Infinite LTB

Infinite ETB

Infinite mana lands you control can produce

Infinite untap of lands you control

Displacer Kitten

Palinchron

Activate up to seven lands you control by tapping them, adding at least {1}{B}{B}.
Cast Mourning by paying its mana cost, targeting Displacer Kitten
Displacer Kitten triggers, blinking Great Whale.
When Great Whale enters the battlefield, it triggers, untapping up to seven lands.
Resolve the Mourning spell.
Activate Mourning by paying {B}, returning it from the battlefield to your hand.
Repeat.

Great Whale

Activate up to five lands you control by tapping them, adding at least {1}{B}{B}.
Cast Mourning by paying its mana cost, targeting Displacer Kitten
Displacer Kitten triggers, blinking Peregrine Drake.
When Peregrine Drake enters the battlefield, it triggers, untapping up to five lands.
Resolve the Mourning spell.
Activate Mourning by paying {1}{B}{B}, returning it from the battlefield to your hand.
Repeat.

Peregrine Drake

Activate any number of creatures you control by tapping them, adding at least {1}{B}{B}.
Cast Mourning by paying its mana cost, targeting any creature you control except Displacer Kitten.
Displacer Kitten triggers, blinking itself.
When Displacer Kitten enters the battlefield, Intruder Alarm triggers, untapping all creatures.
Resolve the Mourning spell.
Activate Mourning by paying {B}, returning it from the battlefield to your hand.
Repeat.

Combos with "Mourning"