If you don't want to make this yourself, you can find the easy-to-use template here.

In this video tutorial, we will show you how to create a realistic Doctor Strange portal using Adobe After Effects. To follow along with this tutorial, you'll need the Trapcode Particular plugin.

To begin creating this effect, prepare a backplate that is color-graded to look like the shot was taken at night. Add some reflections to make your scene look realistic. You can download the backplate to follow along with the tutorial using the same footage.

Once you have the backplate ready, set up your portal VFX composition in a new solid layer. Watch the video to learn more about this effect, or check out the pre-made elements on this website if you don't have the Trapcode Particular plugin or if you want to skip the tutorial.