Caeruleam is a rare and powerful substance that helped fuel Quelmar's industrial revolutions in the PR era starting in the 800s after the return of dragons.
About
Caeruleam is produced naturally in a gland found in the glottal sacs of a small number of creatures, most notably the great Blue and Bronze dragons.
Uses
When the caeruleam producing sac is removed from a living creature, it will lose all power production within a day, but methods were soon discovered to preserve the sack and keep it generating lightning well past the death of the sac's original owner.