4 Knight Of Dusks Shadow The Best Bang For Your Black One of the cheapest ways to prevent lifegain is with the two-mana Knight of Dusks Shadow
For example, if two creatures you control with lifelink deal combat damage at the same time, Heliod's ability will trigger twice
Finally, it requires no faction commitment so it can be run in any deck
The curve is high, so some extra ramp would help, but overall the synergy is tight
She punishes every card that your opponents draw for two life, while gaining you two on your own draws, turning the natural card advantage your commanders generate into a clock
Ruhan of the Fomori and Numot, the Devastator These Legends provide alternate red/blue/white Commanders for your deck but dont really play into the themes that Zedruu suggests