Modron

Modron: MOHD-ron
Welsh, derived from "Matrona," Gaulic Celtic mother goddess, meaning "Great Mother."

Daughter of Afallach, king of the Otherworld Avalon. In this aspect, she is identifiable with Morgan le Fay, and the Lady of the Lake. She is a Mother Goddess, in this case mother of Mabon ap Modron, supernatural hero and seasonal god, and thus identifiable with Rhiannon--both lost their sons at three days old, and were punished for it.

Based upon "Pa Gwr," she is thought to have been impregnated (gods don't really get married, though they say they do) by a hypothetical god Meldos or Mellt. There has yet to be any literature produced to prove there was a god called Meldos or Mellt.

In some Welsh texts, she is said to be the wife of Urien of Rheged, some texts say Uriens of Gorre (the latter being a fictional version of the former, who was a historical king in North Britain). As such, she is replaced by Morgan le Fay in Le Morte d'Arthur.

In TSR/Wizards of the Coast's Planescape Campaign Setting for Dungeons and Dragons, the modrons are a race of robots from the clockwork plane of Mechanus. They first appeared in Monster Manual 2, for Advanced Dungeons and Dragons First Edition, where their home plane was called Nirvana.

The fifteen ranks of modrons, in increasing order of importance, are:

Base modrons:

Monodrones, the Workers
Duodrones, the Labourers
Tridrones, the Administrators
Quadrones, the Standard, the Sergeants
Pentadrones, the Enforcers

And hierarchs:

Decatons, the Lieutentants
Nonatons, the Comissioners
Octons, the Governors
Septons, the Nuncios
Hextons, the Generals
Quintons, the Mediators
Quartons, the Overseers
Tertians, the Judges
Secundi, the Viceroys
Primus, the One and Prime, supreme lord of Regulus

Any modron who becomes chaotic and thus a rogue is translated to the rank of quadrone and expelled from Mechanus. Every so many cycles of Mechanus (accounts vary as to how many), a large army of modrons assembles and goes on a sort of pilgrimage right around the Outer Planes. This event is known as The Great Modron March, and provides the background for the adventure series of the same name. There are not yet 3e statistics for Modrons, but they are mentioned in the new Manual of the Planes.