Animation Module + Scion of the Swarm + Ashnod's Altar + Soul's Attendant
Animation Module
Scion of the Swarm
Ashnod's Altar
Soul's Attendant
Infinite +1/+1 counters on a creatureInfinite colorless manaInfinite creature tokensInfinite death triggersInfinite creature ETBInfinite lifegainInfinite lifegain triggersInfinite creature LTBInfinite creature sacrifice triggers
How it works
Cause a creature to enter the battlefield under your control.
Soul's Attendant triggers, causing you to gain 1 life.
Scion of the Swarm triggers, putting a +1/+1 counter on itself.
Animation Module triggers, causing you to pay 1 to create a 1/1 Servo artifact creature token.
When the Servo enters the battlefield, Soul's Attendant triggers.
Holding priority, activate Ashnod's Altar by sacrificing the Servo, adding CC.
Resolve the Soul's Attendant trigger, causing you to gain 1 life.
Repeat from step 3.
This clever loop sets off a cascade of triggers starting from any creature entering the battlefield, which Soul's Attendant uses to gain you 1 life. That lifegain immediately rewards Scion of the Swarm with a +1/+1 counter, which in turn wakes up Animation Module to let you buy a Servo token for the meager price of {1}. Ashnod's Altar then steps in to turn that freshly minted Servo into two colorless mana, leaving you with a profit of mana while feeding the very altar you need to repeat the process infinitely.