The Ring of Light's other ability manifested as their current state: Dark Vision—true Dark Vision. Or, to put it another way, eternal light. It was a high-priority state, allowing clear vision even in the deepest darkness. This was a very high-tier ability, infinitely stronger than the Dark Vision they could currently achieve through Spells.
For instance, the Dark Vision they used via Spells in the lightless environment Chadite created only allowed them to see about a meter ahead. However, the Dark Vision granted by the Ring of Light was completely unaffected, as if it were daytime. The same held true for darkness created by other Spell effects or Treasure abilities. Its primary ability was to control and strengthen light.
"Can it enhance your original core Spell?" Alka asked.
