Arcane eye

Arcane eye was an arcane divination spell that allowed its caster to spy on things from a distance.

Effect
The spell would create an invisible floating eye, which would give a mental image to the caster whenever it was dark and within 30 feet. The eye could travel 30 feet from its caster and could enter holes as small as 1 inch (2.5 centimeters) in diameter. The eye would move as per the caster's demands of it.

Components
A bit of bat fur.