Cast Carnage by paying {2}{B}{R}. When it enters, it triggers, returning Glasspool Mimic from your graveyard to the battlefield as a copy of Carnage.
Put Glasspool Mimic into your graveyard due to the legend rule.
Glasspool Mimic's enter-the-battlefield ability triggers, returning itself from your graveyard to the battlefield as a copy of Carnage.
Repeat from step 2.

Infinite LTB

Infinite ETB

Infinite death triggers

Carnage, Crimson Chaos

Glasspool Mimic // Glasspool Shore

Cast Saw in Half by paying {2}{B}, destroying Carnage and creating two token copies of it with reduced power and toughness.
Put either Carnage token into your graveyard due to the legend rule.
When the Carnage tokens enter, they trigger, returning up to two applicable cards from your graveyard to the battlefield, including Activated Sleeper if it's in your graveyard.
If Activated Sleeper was not returned in step 3, cast it by paying {2}{B}. Regardless, choose to have Activated Sleeper enter as a copy of Carnage.
Put Activated Sleeper into your graveyard due to the legend rule.
When Activated Sleeper enters, it triggers, returning itself from your graveyard to the battlefield as a copy of Carnage.
Repeat from step 5.

Saw in Half

Activated Sleeper

Cast Carnage by paying {2}{B}{R}. 
When Carnage enters, it triggers, returning Loyal Retainers from your graveyard to the battlefield.
Activate Carrion Feeder by sacrificing Carnage.
Activate Loyal Retainers by sacrificing it, returning Carnage from your graveyard to the battlefield.
Repeat from step 2.

Infinite +1/+1 counters on a creature

Infinite sacrifice triggers

Loyal Retainers

Carrion Feeder

Cast Carnage by paying {2}{B}{R}. 
When Carnage enters, it triggers, returning Saffi from your graveyard to the battlefield.
Activate Saffi by sacrificing it, targeting Carnage.
Activate Carrion Feeder by sacrificing Carnage.
When Carnage dies, Saffi triggers, returning Carnage from your graveyard to the battlefield.
When Carnage enters, it triggers, returning Saffi from your graveyard to the battlefield.
Resolve the Carrion Feeder ability.
Repeat from step 3.

Combos with "Carnage, Crimson Chaos"