The Secret of the Ancients
The Secret of the Ancients is the end goal of the CrossWorlds MMO, and drives much of the plot of this in-universe game.
The Message of the Sky
The Message of the Sky was something sent by the Gods of Shape to the Ancients, intended as a reward for their accomplishments. It was wrapped in an envelope of rock and ice by Di'aro, guided by G'oni and accelerated by K'win. It reached Shadoon as a meteor, and crashed on the surface, creating the crater that now houses the Ku'lero Temple. It was stated that receiving the Message of the Sky was somewhat urgent for the Ancients. Although the exact nature of the Message is never spelled out, it is implied to be the large Ferro ball powering the Secret of the Ancients.

The Secret of the Ancients
The Secret of the Ancients is the end goal of the Track of the Ancients. Operation Trackwalker has been working to uncover and follow the Track in order to rediscover the Secret, presumed to contain highly valuable and useful information left by the Ancients.
The Secret is finally uncovered at the end of the Ku'lero Temple in the A New Home DLC. It is a massive portal to another world, through which the Ancients left Shadoon. The presence of this portal serves in-universe to set up a sequel to CrossWorlds, CrossWorlds: New Horizons.
