When paired with edict effects that can force each player to sacrifice a creature, Vren is going to create an unstoppable board very quickly, and that's ignoring all the death triggers that will occur as players attack and block each other's creatures
Then you can simply sacrifice them to something like Goblin Bombardment or just have a card like Warstorm Surge deal damage to your opponents
It is a cheap and efficient card draw source that, over the game, will provide for you so long as you can continue to make the one token per turn that it needs, which we have a number of options for
Dragapult (006/015) Despite looking like an interesting pull from a competitive perspective, the Dragapult promo from the Dragon Discovery list isnt too valuable
And a ton of commanders actually have enters-the-battlefield abilities (such as Godo, Bandit Warlord, Bladewing the Risen, Prime Speaker Zegana, or Venser, Shaper Savant)