This egg was only available in Egg Cave's Cash Shop Park for Earth Day 2014 (April 22).
Ryby eggs will only hatch if they are incubated upon ice. Only the bottom quarter of the egg should be encased in ice. If more than half of the egg is covered with ice, it will not hatch. Ryby eggs also dissolve into water if they get too warm.
Rybies have the capability of living in both salt and fresh water. This still baffles the Science and Research Center in Ark City to this day, as no other living organism besides Unchagas has ever exhibited this ability nor are there any biological indications as to why they can do this.
Considering their adaptive abilities, you might think that Rybies thrive in terms of population. Quite the contrary: Rybies require a finely-tuned, pure environment in order to live. This means that Rybies are sensitive to water pollution and any slight changes in the environment. As a result of this, Rybies are often used as a symbol to bring awareness to the environmental changes happening on Ark.