What the hell is this?

So i was spectating a recent match of and i found this right above my champion while walking into lane. It looked like an floating animation (kind of like the CTRL + 6 Mastery emot) but had a different design. It randomly appears, so far it only works on the Jade Fang Cassiopeia skin. So far, out of 7 times of trying in custom games, it has appeared only thrice. Care to explain what this signifies? It's killing me -_-
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