Mortus Lungfish Warframe Animation?

[YUMMYGORE]

I was recently going through one of the public lobbies and saw a player with an animation of a bunch of glowing fish swimming around them. I wanted to ask where they got it but they were idle, and nobody else answered. Can someone help tell me where I can get this/ if it was a limited event thing?

[McCIoud]

You might have been seeing the Nezha Prime accessory ephemera

[MqToasty]

Is this the one?

https://warframe.fandom.com/wiki/Ephemera#Crania

That's one of Teshin's offerings for Steel Essence.  You need to farm those from the Steel Path, which is essentially "Hard Mode" you unlock once you clear the Star Chart.  Thankfully, Teshin always has these on offer, although they do cost quite a bit.