While I was farming for Alamaric Sniper and Ghost Dancer souls, I had something happen where it looked like a Sniper was going to give me a soul, but I didn't actually get one. Instead, this red magic circle-looking thing was left behind in the air for a few seconds, along with a pair of wings. Eventually, the wings disappeared, and the circle expanded and faded away.
I only had 7 Sniper souls at the time, so it wasn't that I was maxed out. I've tried researching it myself, but searches about "magic circle" tend to lead to Magic Seals, and searches about souls not dropping tend to lead to complaints about drop rates, so I haven't had any luck. If it matters, I'm playing on DeSmuME 0.9.7.
Is this an actual part of the game, or just a glitch of some sort?
In response to the Arc Demon suggestion: I've found a Dawn of Sorrow Arc Demon sprite sheet on this site. While they also use red magic circles, the designs aren't very similar, so I'm afraid that can't be it. Among other things, this circle has a star in the center, while the Arc Demon one does not.