This effect was inspired by Elden Ring Carian Magic, especially the Comet Azur and Carian Phalanx. Accordingly, I imagine something very powerful and shiny but with some drops of dark magic for this effect. For that I created ghosts who get a target and then attack rapidly. In this project I used mostly Unreal Engine Niagara and some Houdini particles.
In my blog there is a couple of words about development of this project.