Halo: The Union a war beyond world's.

the Halo universe was never prepared for the UNION.

2552.

humanity is fighting for survival against the Covenant.

worlds are falling. Fleets are being destroyed. The war seems impossible to win.

then something appears beyond the known boundaries of human space.

a fleet.

not Covenant.

Not UNSC.

Not Forerunner.

something else.

the UNION an ancient interstellar civilisation from another universe has crossed into Halo's galaxy.

with an enormous military, dozens of species, technology beyond anything the UNSC has encountered and a history stretching across unimaginable ages, the union could change the balance of the entire war.

but the Covenant isn't the only thing watching.

the flood is waiting.

ancient powers are awakening.

and something might have followed the union through the void.

two universes. One galaxy.

and a war that neither side was prepared to fight.