Invium

The Invium River, also known as Vena Invia (River Invia) or Venum Necta (The Great River), is the second longest river and the largest river in terms of annual discharge. The total length of the river is around 9,000 kilometers, making it the second longest river in the world.

Beginning at the confluence of the rivers Lunavia and Victinium at Luna Nexa, the river transverses the entire continent of Irridia to join the Strait of Invia at Invia Nova. The river discharges, on an average, 137046.55 TMCs of water, making it the largest river in terms of discharge. Two of Irridia's iconic cities, Luna Nexa and Invion, are situated on the banks of the Invium.

Etymology
The river is first mentioned by the name Invium in the 2nd chapter of the Irrenix Ultimus, being called upon as,

"Invium venum aurum vium avensium nivenis in venum veretios nox von impetrix rivius aurae no virivinatis" 

Translation:
 " O, Invium, the river greatest, flowing from the grand West to the great East, thy scion plead thee to nourish them as they set forward on the path that leads to their destiny."

The root of the name Invium is not clear, but a possible root may be in in (flow, move).

The Invium is the namesake for the city of Invion and the state of Invia.

Source
The Invium originates at the confluence of the Lunavia and the Victinium at Luna Nexa. The Irrenix Ultimus contains a legend about the river:

"As the Rain deserted the continent, Irridia, once lush with jungles, was forsaken by its own kin. But the kingdom of Luna, ever faithful to the motherland, tried to the limits of their potential to re-establish the flow of the rivers. Pleased by their efforts, the Earth willed for the Victinium, the only river that still flowed, to reverse its course to meet the Lunavia, thereby giving rise to the Invium. As the Invium rushed across the land, every bit of soil that had lost all life was rejuvanated and glowing with the glory of life."

The source of the Victinium has been traced to Victini Strata, where the ice from the Virsix Glacier melts to give rise to the stream. However, the source of the Lunavia has long been known to be at Luna Magna, but it wasn't until the early 21st century that the true source was found to be at a natural spring 6 kilometers below Luna Irixa, and then flows upward to emerge as the Lunavia at Luna Magna.