What are soulo shells on fusion fall

The soulo shells show up around the chains holding the tree house down (the ones that have operatives at), at ground level. Usually, the shells have a very long period of spawning, longer than the required 60 secs. Rumored, the shells glitch up and don't ever show up, and usually is fixed when an update happens.
interestingly, the soulo shells and the soulos are only relevant to the said mission, "sector defense" where you get the numbuh 2 nano.