Ammonax, Encased Kraken

Some days, you just need more shellfish, son.

Ammonax is a giant ammonite made by an intergalatic, but water-bound, race.  They settled down on Earth millions upon millions of years ago and established Earth as a vacation zone.  They found Earth comparatively beautiful, seeing how it had much more diversity than their own ocean planet.  But, their vacation soon became a nightmare, as giant monsters threatened the buildings and structures they had set up!  To protect themselves, these 'Atlanteans', if you will, made their own giant monsters using Earth-creature bases.  Ammonax was one of them.  But, as it turned out, they couldn't get the giant shellfish to do anything.  So, in retaliation, they put him in suspended animation for his general laziness, before they were destroyed by the attacking monsters.

Cue Modern-day Earth, where the ruins of the Atlantean's vacation hotspot have been discovered.  A human expedition trip uncovered and freed Ammonax, and discovered the story of the Atlanteans.  And now, there is a giant floating ammonite wandering around, with not much to do.

Ammonax is not only a giant ammonite, he floats too.  Yes, above the water.  This is because when he was created, the Atlanteans generated a special organ that generated a lighter-than-air gaseous chemical that became acidic if it came in contact with Earth's atmosphere.  Ammonax can easily control his floating height, but there is a natural limit to how high he can float.  Ammonax can also easily weaponize this gas, using it as a cone, a jet to propel backwards, or packing it into an explosive bubble.  Ammonax also fights by wipping with his tentacles, and moves along the surface by using his four lower tentacles to pull himself along.

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Yes, this is finish!  I like the background I did, but I do think the rest needs practice.