Ebondeath from your graveyard by paying ({2} magic symbol) ({B} magic symbol) ({B} magic symbol) .
Geralf's first ability triggers, creating a 2/2 Zombie Rogue creature token.
When the Zombie Rogue enters the battlefield,
Geralf's second ability triggers, putting a number of +1/+1 counters on the Zombie Rogue equal to the number of other Zombies that entered the battlefield under your control.
When
Ebondeath enters the battlefield,
Geralf's second ability triggers, putting a number of +1/+1 counters on
Ebondeath equal to the number of other Zombies that entered the battlefield under your control.
Activate
Phyrexian Altar twice by sacrificing the Zombie Rogue and
Ebondeath, adding ({2} magic symbol) .
When the Zombie Rogue and
Ebondeath die,
Pitiless Plunderer triggers twice, creating two Treasure tokens.
Activate the Treasures by tapping and sacrificing them, adding ({B} magic symbol) ({B} magic symbol) .
Repeat.
Notes
This combo will steadily put more +1/+1 counters on
Ebondeath and the Zombie Rogue token, eventually resulting in an infinite number of them.