Radiant Arc Effect

Does anyone know how to get the Radiant Arc effect? The current effects in the MTX shop are kind of underwhelming, basically color changes rather than any real nifty effect.

And maybe a suggestion for a future MTX, I think a sunprism effect in the style of Herald of Lightning's interpretation would be wicked.

Lastly, where my curse MTX at? Gimme more opportunities to throw money at you guys :P