It's an animated procedural glowing material. There are two empty objects used as controls for pattern and brightness change, brightness curve is only a reference that allows to see more accurately how it's going to change in time.

I've used external environment texture, here's the link:

http://timothykurek.com/wp-content/uploads/2017/10/dark-background-vectors-photos-and-psd-files-free-download-on-dark-black-background.jpg

And here's the animation itself:

https://vimeo.com/251729166