Activate Ashnod's Altar by sacrificing the persist creature.
When the persist creature dies, its persist ability triggers, returning it from your graveyard to the battlefield with a -1/-1 counter on it.
When the persist creature enters, Warden of the Grove triggers, putting a +1/+1 counter on the persist creature.
Repeat

Infinite creature ETB

Infinite creature LTB

Infinite colorless mana

Infinite death triggers

Infinite creature sacrifice triggers

Persist Creature

Ashnod's Altar

Warden of the Grove

Activate a creature using Grist's first loyalty ability by putting a loyalty counter on it, causing you to create a 1/1 Insect creature token and mill a card, and then put a loyalty counter on the creature and repeat the process if the card was an Insect.
When the Insect enters, Warden of the Grove triggers, putting a +1/+1 counter on the Insect. This causes it to gain Grist's abilities due to Agatha's Soul Cauldron.
Repeat from step 1 using the Insect token instead.

Infinite self-mill

Infinite creature tokens

Agatha's Soul Cauldron

Grist, the Hunger Tide

Cast Murderous Redcap by paying {2}{B/R}{B/R}.
When Murderous Redcap enters the battlefield, it and Warden of the Grove trigger.
Resolve the Warden of the Grove trigger, putting a +1/+1 counter on Murderous Redcap.
Resolve the Murderous Redcap trigger, dealing an amount of damage to itself equal to its power.
Murderous Redcap dies as a state-based action due to having 0 toughness.
Murderous Redcap's persist ability triggers, returning it from your graveyard to the battlefield with a -1/-1 counter on it.
Repeat from step 2.

Murderous Redcap

Activate Skirk Prospector by sacrificing Scuzzback Marauders, adding {R}.
When Scuzzback Marauders dies, its persist ability triggers, returning it from your graveyard to the battlefield with a -1/-1 counter on it.
When Scuzzback Marauders enters the battlefield, Warden of the Grove triggers, putting a +1/+1 counter on Scuzzback Marauders
Repeat.

Infinite red mana

Skirk Prospector

Scuzzback Marauders

Activate Skirk Prospector by sacrificing Putrid Goblin, adding {R}.
When Putrid Goblin dies, its persist ability triggers, returning it from your graveyard to the battlefield with a -1/-1 counter on it.
When Putrid Goblin enters the battlefield, Warden of the Grove triggers, putting a +1/+1 counter on Putrid Goblin.
Repeat.

Putrid Goblin

Activate Tooth and Claw by sacrificing two other creatures.
When the creatures die, One with the Kami triggers for each modified creature that died this way, creating a number of 1/1 Spirit creature tokens.
When the Spirit token(s) enter, Warden of the Grove triggers that many times, putting a +1/+1 counter on each Spirit.
Resolve the Tooth and Claw ability, creating a 3/1 Carnivore creature token.
When the Carnivore token enters, Warden of the Grove triggers, putting a +1/+1 counter on the Carnivore token.
Repeat.

Tooth and Claw

One with the Kami

Cast Dargo from the command zone by paying {R}.
When Dargo enters the battlefield, Warden of the Grove triggers, putting a +1/+1 counter on Dargo.
Activate Dargo using Wild Cantor's ability by sacrificing it, adding {R}.
Choose to return Dargo from your graveyard to the command zone.
Repeat.

Infinite storm count

Infinite commander casts

Dargo, the Shipwrecker

Wild Cantor

Activate Yidaro's cycling ability by paying {1}{R} and discarding it.
Yidaro triggers, putting it from your graveyard onto the battlefield.
When Yidaro enters the battlefield, Warden of the Grove triggers, putting a +1/+1 counter on Yidaro.
Resolve the Yidaro cycling ability, causing you to draw a card.
Activate Yidaro using Grinning Ignus's ability by paying {1} and returning Yidaro from the battlefield to your hand, adding {C}{C}{R}.
Repeat.

Combos with "Warden of the Grove"