Learning VFX and Shaders

I am currently in a class, and trying to pratice my VFX skills. I am making a vfx for the spell shadowsword from dnd, just posting what I have so far hoping for some helpful critques. I would love any help with my shader, I am currently such on how i can stop it from disappearing and not sure if that is possible with just the node shaders in unity. Since I use cosine time it will just reappear and then disappear