Where there's a Nautilus, you can be sure there will be Argonauts nearby. Their hardiness ability to lock a Battleframe to the ground make them undesirable to deal with to say the least.
The origin of the Nautilus found in the coastal areas of New Eden stand as a great mystery to Earth’s scientists. Although they share their name with the mollusks that are native to Earth’s warm equatorial seas, that is where the similarities end. The Nautiluses found around Coral Forest are massive by comparison, averaging greater than two-meters in height, with some growing large enough to dwarf a Battleframe. However, how the Nautilus grew to such a size remains a mystery.
Several theories about the origin of the Nautilus have been circulated. One hypothesis is that the Nautilus is a previously undocumented species native to Earth that was forced to migrate to the surface after the arrival of the Melding. Another theory, which has been adopted by most scientists that have studied the creatures, states that these Nautiluses are the result of undocumented experiments that spliced together the genes of the smaller nautilus pompilius from Earth, and the Giant Shore Crostin that were brought back to Earth from their native Alpha Prime. This hypothesis is supported by the observations of the Nautiluses’ incredibly volatile behavior.
Nautiluses exhibit highly aggressive behavior and can be quite dangerous when antagonized. Because they are slow to travel from one location to the next, they are highly territorial and quick to lash out at any perceived threat. A Nautilus will use their tentacles to grip their foes, holding them in place while they spew an acidic ink on them. On occasion, a Nautilus will also be assisted in combat by smaller creatures called Argonauts. Very little is known about these tiny creatures, but it has been witnessed that when Nautiluses are attacked, Argonauts will swarm the aggressor, bringing the wannabe predator down and bringing the remains back to the Nautilus for food.
When the Nautilus is feeling threatened, it will bury its vulnerable underbody in the ground while using its large, nearly impervious upper shell as a shield. Against other predatory wildlife, the shield is practically impenetrable and can even withstand concentrated fire from Accord weaponry. When confronted by a Nautilus, Accord soldiers are told to aim low and, if possible, use weapons with an area-of-effect.