I made this in all of 5 minutes on my phone because I’m busy, so apologies its low effort. I’m also in the middle of an edit, so any other VFX people feel free to explain this better than me.
This effect can be done practically or in after effects easily.
If its a practical effect all one would have to do isolate the frames of the ink they would want to use for each portion and apply it as a screen over the footage.
If you notice the portal changes shape with each frame dramatically, very little of the form is carried frame to frame.
So my best guess is who ever made this took frames from a practical effect and applied them as a screen on these few frames.
If its entirely done in after effects, it can be done with templates.
Also, you have seen this effect in every thing from 2001: A Space Odyssey, Tree of Life, opening credits of True Detective and more.
Also given that this video came out around the same time as Tree Of Life & True Detective it would make sense who ever made this connected this effect to making the portal in this shot.
Anyway my two cents as a professional with 15 years making images with cameras in the real world and on a computer.