The blade of the sword is actually just made from the default spatial material using the following properties
- Metalic (Metalic at .7, Specular at .31)
- Roughness (Roughness set at 0)
- Emission (Energy at 2.1)
- Refraction (Scale at .13)
For breaking the sword I used the Grow parameter on the material this is the code 
It's surprisingly simple, the rest of the effects are just Godot's particle system. Hope this helps! (Sorry if you don't use C#, it shouldn't be too hard to translate)