Activate Phyrexian Altar by sacrificing Persistent Specimen, adding {B}.
When Persistent Specimen dies, Bhaal triggers, putting a +1/+1 counter on Cryptic Trilobite and goading it.
Activate Cryptic Trilobite by removing a +1/+1 counter from it, adding {C}{C} that can only be spent to activate abilities.
Activate Persistent Specimen by paying {2}{B}, returning it from your graveyard to the battlefield tapped.
Repeat.

Infinite death triggers

Infinite ETB

Infinite LTB

Infinite sacrifice triggers

Bhaal, Lord of Murder

Persistent Specimen

Cryptic Trilobite

Phyrexian Altar

Activate Ashnod's Altar by sacrificing Persistent Specimen, adding {C}{C}.
When Persistent Specimen dies, Bhaal triggers, putting a +1/+1 counter on Crystalline Crawler and goading it.
Activate Crystalline Crawler's first ability by removing a +1/+1 counter from it, adding {B}.
Activate Persistent Specimen by paying {2}{B}, returning it from your graveyard to the battlefield tapped.
Repeat.

Crystalline Crawler

Ashnod's Altar

Combos with "Persistent Specimen"