Your devotion to black is at least three, or you have at least two opponents.
({2} magic symbol) ({C} magic symbol) available.
Steps
Activate Eldrazi Displacer by paying ({2} magic symbol) ({C} magic symbol) , blinking Gray Merchant of Asphodel.
When Gray Merchant of Asphodel enters the battlefield, it triggers, causing each opponent to lose life equal to your devotion to black, and causing you to gain that much life.
Workhorse triggers, putting at least three +1/+1 counters on itself.
Activate Workhorse three times by removing three +1/+1 counters from it, adding ({C} magic symbol) ({C} magic symbol) ({C} magic symbol) .
Repeat.
If your devotion to black is at least four, this combo nets infinite +1/+1 counters on Workhorse and colorless mana.
Results
Infinite +1/+1 counters on Workhorse.
Infinite blinking.
Infinite colorless mana.
Infinite ETB.
Infinite lifegain.
Infinite lifegain triggers.
Infinite lifeloss.
Infinite LTB.
Infinite blinking of creatures you control except Eldrazi Displacer.