1)slash effect 2)area skills like dota2 crystal maiden ulti and first skill 3)over an enemy skills example dota2 crystal maiden second skill

how they make in opengl

i know opengl billboards way and texture atlas i can make basic flame effect with using these 2 way together. But how they make others ? area skills are 3d model animation ? then its texture is changing every frame? over an enemy skills can 3d model i think? how they make skills transparent ? with glblend ? what is best way to make them sorry for bad english i searched but i couldn't find any suggestion help please im using c++,sdl,opengl