So, the Precursors are the most advanced, sophisticated, and mysterious species in the entire Halo Universe. They created the Domain, a repository network that holds 100 billion years of information. Across the Universe, the Precursors seeded life, including the Forerunners and us Humanity in the Milky Way. The Forerunners eventually rebelled against the Precursors, with those still alive turning themselves into dust to regenerate later on. However, this dust eventually deteriorated and the Flood would soon come about, their current form. In Silentium, Forthencho tells the Librarian what the Primordial revealed to him,
The Precursors lived in many shapes, flesh and spirit, primitive and advanced, spacefaring and locked to their worlds ... Evolved over and over again, died away, were reborn, explored, and seeded many galaxies ...
So they live as many different species time and time again, with the Flood their current form in our Universe. I believe that the Precursors don't actually exist in our Universe, but actually outside it, in other dimensions. What makes me believe this even more is what's been revealed about the star roads, a Precursor construct,
Untouchable and perpetual filament of neurophysical energy woven between dimensions by the Precursors. Their shadows in real space took the appearance of multi-kilometer-thick filaments of strange matter.
Precursor constructs are woven between dimensions, with what's in our Universe being just a shadow of their true nature and purpose. With this, it makes me believe that the form the Precursors take in the Universe are just vessels, and when they die they just go back to where they really exist, and eventually go back into the Universe as another species. With them creating the Universe, I think it could be very likely. They had info in the Domain that stretches back 100 billion years, and the Universe is 14 billion years old. Also, it's Forthencho tells that Librarian that he was informed that the Precursors have been around before even the stars were formed. This makes me believe that the Precursors actually created the Universe itself. Just a theory of mine, what do you all think?