Im kind of new to this. Ive done some simple effects with distorting UVs and Panning Textures and some hand painted Textures as Billboards, but this seems really out of the scope of my understanding. All i know that the Mesh is a sort of cone shaped Hemisphere that starts at the tip of the Weapon. If anyone could help me it would be much appreciated. Thank you 
It looks like it’s using multiple meshes of different sizes, the dark one being the smallest and the white one the biggest. If you create a mesh like a cylinder or cone that has the UVs unwrapped from top to bottom, or in the case of the example the cylinder is horizontal so it’s left to right, then you can do a lot with scrolling the UVs.
Then you add a texture to it and use that to define where the cylinder is visible and where not. If the texture already has alpha, you could just use that. But if you use a normal color one you could say that if the red value of the texture is below x, then don’t show any alpha. If you get this far, there is already a lot you can do and experiment with it.
I’m pretty sure the only 3D mesh in this is the circular ring around sin, everything on his flag is a hand drawn flipbook,
its actually the mesh i described. you can see it from some other angles in the game, especially when you break the wall, but it looks really hand drawn right?
I think the movement and dissolve look too even for a flip book. Of course someone could always draw it like that, but the advantage of a hand drawn effect would be nicer movements and variety.
It can be both a 3D mesh and flipbook, but these are 100% flipbooks. I recommend checking out this gif in PureRef frame by frame. You can cheat it with dissolve maps but you won’t get the same control.