hive fleet Coronoid was entering the Coronoid system while the imperium had begun to explore it. Coronoid was originating from hive fleet Kraken and was one of the splinters that was seperated from Kraken. it was named after the system it appeared in. Coronoid clashed with the imperial defenders in a large battle that did last for many Months until the imperial forces struck the fleet down. it crashed on the surfice of the planet Protaan. Coronoid was recorded as defeated.

shortly after the defeat of coronoid, a new threat arrived and unleashed the mankind's worst fears. the hive fleet named Xeno arrived from outside the galaxy, it defeated the imperial forces and destroyed those who didnt retreat. it totally consumed the planet Zerge, and several of it's moons and neighboor planets. but Xeno ignored Protaan somehow, exept for staying around it a few days before moving forth into the imperial borders.

a while without activity passed by in the coronoid system. but while a imperial fleet was on its way to investigate the system since the xeno attack they faced a small fleet of hive ships approaching from the system. the imperial fleet recorded this,as far as they knew, the same fleet that was destroyed on protaan about a year ago. after engaging the hive ships they was ambushed by several hive cruisers from all directions, the imperial fleet was cripled and consumed. Coronoid did continue to attack isolated worlds and slowly continued to grow into a large fleet.

it's well known that if tyranid fleets face eachother they will fight, and the stronger fleet gains all the biomass. but, Coronoid have in several occations been facing Xeno. the first time coronoid was battling a imperial exploration fleet. and suddenly Xeno arrived from nowhere, the imperial forces was trying to retreat to let the tyranids battle it out, but unexpected they both attacked the imperial fleet, a few ships reported about this strange "alliance" between the fleets. it was later reported that both passed eachother without doing any harm. there are theories that Xeno took full controll, or made a bond between them. and maybe even was responsible for ressurecting Coronoid for a greater purpose...

just like Xeno, Coronoid seem to sphread cults through the galaxy lake a rapid plague. the cults worships the tyranids and starts civil wars to make planets easy prey. they hope to reach a greater purpose once they themselves gets devoured by the tyranids. and they are right at some points. the cults are infesting both civil populations and fulkl regiments of the imperial guard alike. there are vast armies and tank companies in the command of the cults sphread over the whole sector of Coronoids path.

once coronoid entered tau space it came across one of the outposts beloning to the T'au sept. it became a fast strike against Coronoid once it exited warp space. the supreme commander T'hor's fleet was in orbit. they destroyed parts of it before it was awakened from its hibernation. full scale war broke out and T'hor was forced to a quick retreat in order to save tau lives, leaving the planet to it's doom. many tau was evacuated, but some got trapped there.