Activate Altar of Dementia by sacrificing Vorapede.
Vorapede dies, triggering itself, Kheru Bloodsucker, and Pitiless Plunderer.
Resolve the Vorapede trigger, returning it from your graveyard to the battlefield with a +1/+1 counter on it.
Resolve the Kheru Bloodsucker trigger, causing each opponent to lose 2 life and you to gain two life.
Resolve the Pitiless Plunderer trigger, creating a Treasure token.
Resolve the Altar of Dementia ability from step 1, causing target player to mill cards equal to Vorapede's power.
Activate the Treasure by tapping and sacrificing it, adding ({1} magic symbol) .
Activate Hex Parasite by paying ({1} magic symbol) , two life and removing the +1/+1 counter from Vorapede, giving Hex Parasite +1/+0 until end of turn.
Repeat.
Results
Infinite death triggers.
Infinite ETB.
Infinite lifegain triggers.
Infinite lifeloss.
Infinite LTB.
Infinitely powerful Hex Parasite until end of turn.