Solaire of Astora is a Knight of Sunlight who will help the player in many different areas. He is a cheerful and powerful knight who does not let the crumbling world affect his mood. He speaks of willingly becoming an Undead so that he could search for his own sun.

He is theorized by some to be Lord Gwyn's firstborn who has relinquished his deity status (hinted at in his dialogue, in which he gazes up at the sky and asks if "they" would see him as a laughingstock), and is described in the Sunlight Medal description; The description states that Lord Gwyn's firstborn "'still watches closely over his warriors", alluding to Solaire's ability to be summoned to aid in boss fights as a Warrior of Sunlight. His armor description states that it has not been blessed with special attributes, reinforcing the idea that he is extremely strong and versatile in combat for other reasons. Additionally, he possesses the Lightning Spear miracle, which is described as "the weapon of the God of War".

Solaire is also thought of being a second chosen undead. He arrives at numerous locations before the player, showing his strength and pure power. Sadly his tale could end due to the light of a certain creature. If the player kills the sunlight maggots Solaire will help kill Gwyn and allow you to link the fire.

Solaire can be summoned to help you with various boss fights throughout the game. If he survives the fight with you, he will give you a Sunlight Medal. If he dies during the fight, you will not receive the medal. ( ͡° ͜ʖ ͡°)