Worm

Known by names such as the World Worm, the Great Worm, or simply The Worm. It is a colossal Purple Worm sleeping in the core of Nexus. The Worm is so massive that when it wakes its writhing and wriggling will completely destroy the Nexus, though even the most pessimistic estimates say this will not happen for at least 10,000 years.

Wormology
Being at the center of the planet, at the lowest layer of the Underdark, any research on the Worm is inherently highly arduous and risky. However people have long recognized the importance of understanding the Worm, resulting in many research expeditions performed by various cultures throughout Nexus’ history, some of which were successful.

However none of this research found a satisfactory explanation for how the Purple Worm got so massive or why it’s in the center of the planet. We do know that it has been there for an extremely long time. Some of the oldest ruins uncovered, such as those left by the Giants before they vanished, depict the Worm.

Unadvised Experimentation
Ancient and simple civilizations have tried various methods to get rid of the Worm in a futile effort to avoid the future apocalypse. However, since the Worm is effectively the core of the planet, if the worm were to disappear, shrink, die and rot, etc. it could cause the entire Nexus to collapse in on itself. Because of this experiments on the Worm are now forbidden in most societies.

The Worm and Religion
Some Kippelian Faithful believe the Worm is a harbinger of the Dystrophy sent to bring utter destruction when we least expect it.

Some Yuan-Ti kingdoms believe the worm is the pinnacle of life, or even the progenitor of all life, and that it is its right as the most powerful creature on Nexus to end the world when it sees fit.

Other scattered cloisters of apocalyptic Worm Cults have also been observed here and there throughout history. Worshipping the Worm as deity or even attempting to prematurely wake it from its slumber.

Invertebrate Idioms
The Worm is commonly used in expressions, or as a metaphor for something real big.

Some examples include:

These kinds of expressions are most popular in primarily Human communities.