What do Wisp corpses look like anyhow?

'm sure we have all made the BIG MISTAKE of attacking a Wisp, only to end up dead in seconds. They throw horrible spells and hit real hard if you get near. Katsienna, Grandmaster warrior, had tried twice to kill one without luck. On the third time she knew exaclty what to expect and finally succeeded after a long battle that took over an hour. To her surprise, the wisp dropped dead as a small blue pearl on the ground and this had to be captured with a screenshot.