Sakashima of a Thousand Faces in hand or in the command zone.
Enduring Scalelord and Cathars' Crusade on the battlefield.
({3} magic symbol) ({U} magic symbol) plus enough mana to pay for commander tax, if applicable available.
Steps
Cast Sakashima by paying ({3} magic symbol) ({U} magic symbol) and commander tax, if applicable, choosing to have it enter the battlefield as a copy of Enduring Scalelord.
Sakashima enters the battlefield, triggering Cathars' Crusade, putting a +1/+1 counter on each creature you control.
Enduring Scalelord and Sakashima triggers.
Resolve the Sakashima trigger, putting a +1/+1 counter on itself.
Enduring Scalelord triggers, putting a +1/+1 counter on itself.
Repeat from step 4.
Results
Infinite +1/+1 counters on Sakashima and Enduring Scalelord.