Warrior of Sunlight

Warrior of Sunlight is a covenant in Dark Souls.

How to join
Talk to Solaire of Astora at the balcony right before the Red Drake. The requirement for joining is 25 Faith - 5 multiplied by the number of times the player successfully complete a co-op as a white phantom. If the requirements are met, then one can pray at the altar to the right of the bonfire behind the Red Drake (otherwise known as the Hellkite Dragon). Leveling up in the covenant requires the offering of Sunlight Medals.

Benefits
Upon joining, players receive the Lightning Spear miracle, and can learn the Praise the Sun gesture. Players in this covenant will have an easier time co-oping with other Warriors of Sunlight, as well as the Princess's Guard and Way of White covenant members. Also, Warriors of Sunlight will have a golden summon sign instead of a regular white summon sign, and appear as gold phantoms instead of white phantoms.

Upon the completion of a co-op boss run, all members of the party (including the Warrior of Sunlight) will receive a Sunlight Medal, giving Warriors of Sunlight further priority over other summon signs with the incentive of further rewards. The sunlight medal award also applies for summoning NPC Warriors of Sunlight (aka Solaire).

Further rewards are granted upon leveling up:

Betrayal Penalties
Players lose access to the Sunlight Spear miracle.