A Vine is the only living thing that can withstand direct sunlight. They grew in the tunnels for millions of years, slowly evolving until they could survive Daybreak. Then they grew rapidly, miles high in a tangle that eventually grew into what is known as the Vinefields. They could even survive the endless onslaught of the Rims storm, Growing outside of the Umbilical and into the NomadLands and eventually into the Oceans as well.
The Vines are arguably the most dominant life form on Sanctum. Where a vine wants to go, it goes. Slowly but surely. For most all of the existence of Sanctum, The vines were completely uncontested.
The vines themselves were thought to be indestructible, They are more sturdy than any material known on Sanctum, they can grow through rocks, metals and even through the Rim
The Vines are the only living thing on Sanctum that can survive the light given from Daybreak.
The Vines themselves are sturdy, not even swaying from the extreme winds in the Vinefields. The Vines are covered in Thorns, the tips of the Thorns are extremely dangerous, a single prick able to drive a Bound into madness before dying of the toxins. However the rest of the Thorn is harvested and filed away to be smoked as a recreational drug known as "Root Thorn".
When a Vine bends oddly and into itself it can shave off a small layer of it's husk. This material is also harvested and is known as "Husk Sheet" This material is often refined and used for books and scrolls.
Civilizations were near impossible to construct on Sanctum, Large sections of the Vinefields floor free of Vines were rare.
And the few attempts to create a stationary civilization always met the same fate. The Vines eventually grew, and overcame.
Starting Point was the first city to try to use the vines themselves to shield their civilization from the rest of the Vinefields. It was constructed at the base of a vine propped up on different mountains on the Vinefields floor. It was crushed after just 15 seasons.
This was the last time a city was created on the Vinefields floor, another city wouldn't be constructed until Drones allowed for Cities inside the Free Mountains.
Because of this the Bound found themselves living in Caravans that wandered the Vinefields for generations. The Caravans walks the surface of Sanctum, at the base of the Vinefields. Circling endlessly until the discovery of The Passage.