The five-headed dragon slotted right into a number of builds within the Commander format
You can use this in myriad ways, like resetting +1/+1 counters, getting another good ETB creature, or clearing a blocker
It's an incredible pump effect, and because it's attached to a creature and not an Instant or Sorcery, you can find it using green's excellent tutor effects
Because you can use the -1/-1 counter to cancel out the +1/+1 counter from the Undying trigger, you can loop two Undying creatures infinitely to draw as many cards as your life total allows
Youll be instructed to take a couple of cards early on in the spirit of staying open, but feel free to cast that spirit out like a priest at an exorcism when it comes time to build
Gnawing Zombie : One generic and one black mana, 1/3 Zombie