The Celestial Jelly is an enemy in Spelunky 2. It is found in the Cosmic Ocean.
Celestial Jellies stand still at the start of the level, always spawning in front of the exit. They will become aggressive when all the small orbs are destroyed in the level, making it very quickly dash in the direction they're facing in and slowly turn towards you. They are very dangerous due to their high speed and ability to destroy you with a single touch, and their infinite health, like the Ghost.
Pop all bubbles until it becomes aggressive. When they are, run away towards the exit. You can't destroy it and you cannot survive a single hit from it.