Skystone is a naturally occurring crystalline element most frequently found at the extreme edges of the earth. So far we know of red or yellow varieties, with yellow being more potent + rare. Red skystone powers the Noble Jury and several Herald ships. Yellow skystone powers all Lounge vessels and Haman's goblin battleships.
Skystone is a high-value commodity which The Lounge devotes many resources towards mining and trading.
“Natural skystone deposits tend to fluctuate when they're being harvested...That, or being drained of energy.”
- ↑ Yaerfaerda, ch. 88