This character, Energy, has a Ben 10 + Avatar Aang thing going on.

According to the law of thermodynamics, Energy can not be created nor destroyed, only change forms.

But the first main forms themselves are "Monsters", that each also have an element attached to them. There are four monsters with each of the four elements. And a fifth transformation for "Heart", which is useless 99% of the time but basically almost-Super Sonic "when loved ones are in danger". That Heart also belongs to the character Kardiá, so her own origin story is wrapped up in this as basic concept as well.

The "one shot" story I'm working on has only one of each monster that Energy faces one by one and obtains a different "form" from. Although, with four elements, only three can be actual "transformations". Since he's "Sonic", Air would be the automatic default. It doesn't help that the core idea for that monster is also inspired by XLR8 from Ben 10, so I think of it as perfect for a basic monster he'll fight, but redundant as a "transformation", so really it's just a White Wisp at best.

But thinking about this through the lens of Sonic, Energy's forms are basically like Elemental Shields crossed with Color Powers, since they're "transformations" but also have that elemental quality as the main thing as well. But also, I still need to properly think through the mechanics of how each transformation will actually work with his base form essentially being Black Knight Sonic.

Between the Fire Shield & Red Burst, and other things, there's a very clear image of what Sonic with "Fire" is like, mechanically, but water and earth don't have as clear of an image and I think that's what's slowing me down. Although there is that "Gray Quake" Wisp, I guess... But the Water Shield just being a bubble that he can Bounce with feels like it's not capturing the full scope of what I'm looking for ... though I guess that'd just be adding Chaos 0 and the Werehog, I suppose.