Comments - beige6

they made the flood

The Precursors were a race of beings preceding and possibly mythologized by the Forerunners, who believed them to be theoretical "Transsentient" beings, having the ability to travel among galaxies and accelerate the evolution of intelligent life. The Precursors achieved a higher level technological advancement than the Forerunners, being Tier-0, or Transsentience on the Forerunners' Technological Achievement Tiers
However in Halo: Silentium the Flood is revealed to be another form of Precursor made via the powder referenced to in Halo: Primordium that was also revealed to be actual Precursor dust. They were annihilated by Ancient Forerunners, who wished to seize the Mantle of Responsibility from the Precursors instead of letting them give it to Humanity. Some Precursors hid while others changed into the dust found by the ancient humans (the latter created the Flood). The Flood attacked humanity for only a short while because the Precursors favored humanity. The Flood/Precursors found humanity worthy of the Mantle and instead traveled to take revenge against the Forerunners.

there 2 Humans one is the unsc and ancient Humans,

The Composers were pieces of Forerunner technology that were created by the Forerunners in order to gain a foothold against the Flood in the Forerunner-Flood War. They were capable of bridging organic life and digital technology together. One was used by the Ur-Didact on ancient Humans, adding to his legion of digitized beings called the Prometheans