Ballad of the Black Flag's fourth chapter ability has triggered this turn.
Mana Needed
({B} magic symbol) ({B} magic symbol) available.
Steps
Cast
Ebondeath from your graveyard by paying ({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
Altar of Dementia twice by sacrificing the Zombie Rogue and
Ebondeath.
When the Zombie Rogue and
Ebondeath die,
Pitiless Plunderer triggers twice, creating two Treasure tokens.
Resolve both
Altar of Dementia abilities.
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.