Purity ring?

Purity ring? - HALO
Purity ring?

1. Symbol of divinity
2. Circle of light around a saint’s head
3. Heavenly aura
4. Circular band, often made of gold or silver, worn around the head as a sign of distinction
5. Angelic headwear
6. Circular decoration on an astronaut’s helmet to reflect sunlight
7. Video game franchise featuring a protagonist with a suit of armor and a “magical” ring.