Style is one of the strong points, unfortunately design is the weaker one. Looks like it could be good, it's an interesting idea, but it's not immediately reading at this size. I just see kind of this mess of rock and yellow magma (edit: energy), rocky arms/legs and yellow hands/torso, and a woman's head. I'm seeing more here as I type this, but it's what you see at first glance that matters. That's what players see. Maybe readability is better when animated but this isn't a good sign.
If you can show the art it'd be great, if not I'll edit working off the sprite.
EDIT:
After squinting at this I saw a mecha girl made of light floating in a pimped-out mecha suit, so that's what I went with. But if I got it wrong by all means correct me.
If it's only on a dark background, sel-out to your heart's content.
More spikes. You have a motif, use it. It's a boss, so if the motif factors into gameplay, there's a functional need to know that. (See Megaman. Actually, see most boss battles.) Take it up to 11.
Changed some palette entries to reflect the energy theme, so made them hotter (you can leave that pun...)
HTH.
EDIT: On the downside, ninja'd, on the upside, got it right
