The place where Sparks first ignite
In ancient times, they appeared as regions that have been metallized and with all the Sparks it was like seeing the night sky on the ground.
In present day, what few Fields that appear, appear as simply fields of glowing lights, as the whole planet has been mechanized.
Spark Fields are how the Transformers first reproduced. They were created by energy pulses from Axion, either saturating a spot of land, or bouncing of a moon, causing a Plasma Storm and then forming. Each pulse deposits Engen and Proto-Matter, creating a field of cyber matter, covered in sparks with Engen pools and crystals forming underneath.
Both Engen and Proto-Matter are harvested to produce new Transformers. Spark Fields, also sit over Engen Mines, where Engen has collected in liquid and/or crystal form. The Moons of Axion are constantly being mined for Engen due to constantly being struck by Axion's pulses