Energon figure

Energon Figures are small power-enhancing mechanisms in Generation 1 continuity

Energon figures are used to activate or magnify systems built into Transformers to give them special abilities.

More advanced Energon figures can be fitted with special-function units to provide summplementary abilities in addition to their basic power functions.

Energon figures appear to unliving mechanisms designed to integrate with their partners.

Energon figures are a product of latter-day UK toy continuity, and featured in no media. The toys, from Japan's Masterforce and Victory were both former Godmasters and Brainmasters.
Overlord (who had relatively primitive energon figures) was later retconned into being an early pioneer of the Powermaster proscess. The Energon figures may represent an early iteration of that technology.

From Teletraan I: The Transformers Wiki, a Wikia wiki.