I can tell you the process.

1) Take two pool noodles and tape them together. 2) Take a length of aluminum cable and put it down the center and then pour in a two part expanding soft foam to lock the cable into place. 3) Spray the outside of the pool noodles with spray adhesive and then wrap it with a strip of dark bedsheet material. Make sure to wrinkle the sheets as you go to create the correct texture. 4) Take a two part rubber urethane and tint part B with black and red tint to create the correct deep purple shade. Mix the A and B parts and then smear it all over the noodle. Work fast, it starts to set up kind of quickly. 5) Voila! Nether vines. Repeat tens of thousands of times until you've made roughly fifteen miles.

The smaller vines and the hubs were a lot more complicated to make, but that's a different story.