Indestructible Reckoner with lifelink that takes damage adds infinite +1/+1 counters to all creatures you control with Heliod or Archangel of Thune in play. Gideon crews Heart for loyalty, provides indestructible to Reckoner or Ballista, or lifelink for free to Ballista. Deafening Clarion grants Lifelink and starts damage chain with Reckoner. Other cards to consider: Boros Charm (grants indestructible)