Introduced in Labyrinth, crafting pylons are a new addition to the Gemcraft Series referring to both skirmishes on fields D4, D10, J4, J10, and G7 along with their existing physical structures on those fields.
Unlike other endurance-like levels, these battles cannot have their wave numbers adjusted, and will continue to deploy untold amounts of monsters until the Pylons are fully charged by tower gems. Fully charged pylons can decimate entire armies; however, shadows are not even harmed. Also, you can beat all waves in these levels (there are 1337 waves in these levels). When you beat all waves, you will complete the level regardless of the charge (To achieve this, you may want to use only traps to avoid charging).
When fully charged, a grey-black hexagon gem appears on the pylon, except in the last level, where the pylons already had a gem on them and lost them in order to craft the new Gem of Eternity.