Cast Shielded by faith by paying {1}{W}{W}, targeting Siona.
Siona triggers, creating a 1/1 Human Soldier token.
Shielded by Faith triggers, causing you to attach it to the new token.
Repeat from step 2.

Infinite creature tokens

Infinite ETB

Siona, Captain of the Pyleas

Shielded by Faith

Give Boros Reckoner lifelink.
Deal damage to Boros Reckoner.
Boros Reckoner triggers, dealing that much damage to itself and causing you to gain that much life.
Repeat step 4 any number of times.

Combos with "Shielded by Faith"