Blood Artist

Whenever Blood Artist or another creature dies, target player loses 1 life and you gain 1 life.

Night's Whisper

Beast Within

Destroy target permanent. Its controller creates a 3/3 green Beast creature token.

Sarevok, Deathbringer

At the beginning of each player's end step, if no permanents left the battlefield this turn, that player loses X life, where X is Sarevok's power.
Choose a Background (You can have a Background as a second commander.)

Sign in Blood

Target player draws two cards and loses 2 life.

Carrion Feeder

Carrion Feeder can't block.
Sacrifice a creature: Put a +1/+1 counter on Carrion Feeder.

Young Wolf

Undying (When this creature dies, if it had no +1/+1 counters on it, return it to the battlefield under its owner's control with a +1/+1 counter on it.)

Raised by Giants

Commander creatures you own have base power and toughness 10/10 and are Giants in addition to their other types.