There was a previous glimpse of a major even in Yori's past moments after a circle spell exploded and destroyed a small cabin he had taken residence in. Found here. Will need to get it updated in the future: http://www.furaffinity.net/view/28144271/
But let's take a few steps back in the middle of when the spell began to crack and explode. Ever wonder what happens when tightly packed together mana ends up breaking apart, crack and explode? Here's a great visual of just that, and you realize that those circles Yori does are very dangerous stuff! (Made even worse when you realize the one behind them.)
Suffice it to say, the sound of a circle spell breaking apart is not something one wants to hear or see. Glass shattering, streams of rainbow bolts of lightning being sent in every direction that are strong enough to cleanly slice through rock and wood! All before a blast of energy sends everything around it backwards as it blows up everything around it in a small area (such as the cabin from above).
It's a miracle that Yoei managed to even survive such a fate, but what happened afterwards...well...perhaps not so lucky.
Regardless, this is an absolutely beautiful image! I love it immensely! It's a very nice style to see Yori drawn in, along with the sheer power the art piece showcases. The colors are wonderful and the simple, but dynamic background looks especially nice! I hope others like it as well!