How would I be able to create the Call feature from "Journey" (or other games like it)

I was wondering if anyone knows a method on how to create something similar to the Call feature from Journey, Sky, Kumo, etc. (Example in GIF link)

It can just be a sphere, I’m just not sure how to implement it

Thank you in advance for any help

It’s just a sphere with a fresnel map in the opacity slot

Thank you for that, that does make the sphere look so much nicer, though I was wondering how to implement the actual mechanic where when you press a button, it spawns the sphere that grows