Niv-Mizzet triggers, dealing 1 damage to an opponent.
Bloodthirsty Conqueror triggers, causing you to gain 1 life.
Lich's Mastery triggers, causing you to draw a card.
Repeat from step 2.
This loop creates a self-sustaining engine by tying damage directly back into card draw and life gain. Once you draw a card to kick things off, Niv-Mizzet, the Firemind deals 1 damage to an opponent, which immediately triggers Bloodthirsty Conqueror to gain you 1 life. That newfound life triggers Lich's Mastery, forcing you to draw a card, which restarts Niv-Mizzet, the Firemind's ping and keeps the cascade spinning infinitely.