({3} magic symbol) ({B} magic symbol) ({B} magic symbol) plus enough mana to pay for commander tax, if applicable available.
Steps
Cast
God-Eternal Bontu either from your hand or from the command zone by paying ({3} magic symbol) ({B} magic symbol) ({B} magic symbol) and commander tax, if applicable.
Endrek Sahr triggers, creating five 1/1 Thrull creature tokens.
The Thrull tokens enter the battlefield, triggering
Carnival of Souls five times.
Activate
Phyrexian Altar by sacrificing two Thrull tokens, adding ({B} magic symbol) ({B} magic symbol) .
Deathgreeter triggers twice, causing you to gain two life.
Resolve each
Carnival of Souls, causing you to lose five life and add ({B} magic symbol) ({B} magic symbol) ({B} magic symbol) ({B} magic symbol) ({B} magic symbol) .
Resolve
God-Eternal Bontu from step 1.
God-Eternal Bontu enters the battlefield, triggering its first ability.
Holding priority, activate
Phyrexian Altar by sacrificing
God-Eternal Bontu, adding ({B} magic symbol) .
God-Eternal Bontu's second ability and
Deathgreeter trigger.
Resolve the
God-Eternal Bontu trigger, causing you to put it into your library third from the top from your graveyard.
Resolve the
Deathgreeter trigger, causing you to gain 1 life.
Resolve
God-Eternal Bontu's first ability from step 8, sacrificing three Thrulls and drawing three cards.
Deathgreeter triggers three times, causing you to gain three life.
Repeat.
Once you have an empty library, you can continue the combo by only sacrificing one Thrull in step 13, and sacrificing the other two Thrulls to