Phantom

 are a gameplay mechanic in Dark Souls. There are two main varieties of phantoms which enter the players world: Summons and Invaders.

White Phantoms
White Phantoms are either other players, or are specific NPCs, which are summoned to the player's world. As a result, they can help the summoner defeat enemies and bosses, until either the area's boss is defeated, the summoned or summoning player dies, or if the summoning player uses the Black Separation Crystal. No rewards, apart from souls, are granted to white phantoms.

Gold Phantoms
Gold Phantoms are distinguishable from other summons by their golden color, which is a result of them being in the Warrior of Sunlight covenant. The purpose of a golden phantom is the same as a white phantom's, however, upon successfully helping the summoning player to defeat the area's boss, they will be rewarded with a Sunlight Medal, in addition to souls.

Red (Black) Phantoms
Red Phantoms, other wise known as Black Phantoms, are the basic type of invading character or player. Their red coloring is caused by the invader either being in the Darkwraith covenant, using a Cracked Red Eye Orb, or being summoned to another player's world through placing a summon sign with a Red Sign Soapstone.

The aim of a Red Phantom is to kill the host whose world they have invaded. Upon the host's death, they are rewarded with liquid humanity.

Blue Phantoms
Blue Phantoms, also known as Spirit of Vengeances, are unique in that they only invade specific people, unlike Red Phantoms. Blue Phantoms are members of the Blade of the Darkmoon covenant, and thus, only invade those who are deemed "guilty". Their purpose is to punish the sinning player by killing them. If they are successful, then they are rewarded with a Souvenir of Reprisal upon the host's defeat.

The player is never invaded by an NPC Blue Phantom in-game, however, they can invade Lautrec the Embraced as part of a side-quest.

List of NPC Phantoms
* Can only be found in the Artorias of the Abyss DLC.