Don't I know it! And sometimes it'll follow you whenever you open up the game anyway. Dunno why it shows up, though.
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Well, my vortex disappeared after the game crashed. But it was cool to have it, especially when the character walked into it.
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It happens when you remote feed a berry while the gym is under attack. I have never experienced it, but the spouse has.
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I haven't remote-fed any of my mons though, and I only have one left in a gym that was still standing last I checked.
Also, sometimes the vortex appears when I'm catching pokemon. But this is the first time it spawned in the world view.
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I've noticed it on mine whenever a Pokémon I have in a gym is under attack.
I recall others posting about similar experiences about a month back.
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Really? Whenever the gym is under attack for my Pokémon, I can't even open up the Gym - I get the "Gym is under attack, please try again later" error. Do you have to be in the Gym before the attack technically begins for this to happen?