Phantom | Dark Souls Wiki

Other players and summoned NPC will appear in your world as phantoms. There are a few different phantom colorations, each one indicating how they got here and whether they're friend or foe. Regardless of what color phantom is in your world, all exits out of the area will be covered by a white fog that you cannot exit out of, summoned phantoms cannot use Estus Flasks, and bonfires will be disabled.

White Phantoms

• Friendly players summoned through the use of the White Sign Soapstone. They help assist troubled players with the boss, and you can summon two at a time.
• Summon sign is white.
• Can only be summoned by human players while the boss of the area (or a boss, in the case of the Royal Woods and Demon Ruins) is still alive.
• Enemies hostile to the summoner are also hostile to the summoned.
• White Phantoms will receive half of the usual allotment of souls for enemies killed, including bosses.
• Healed by Estus Flasks used by the host.
• NPCs will appear as intangible ghosts to the white phantom, to prevent them from attacking them and messing up the summoner's world. This also means it's impossible for summons to assist in battles against NPCs.
• Can be dismissed with the Black Separation Crystal, although this can be considered impolite amongst players.

Gold Phantoms

• Same as white phantoms, but specific to members of the Warrior of Sunlight covenant, a co op oriented faction.
• Summon sign is gold.
• Generally preferable for co op because of their speciality in dedicated co op play, and because server preference bumps up gold phantoms, making them easier to summon.

Dark Phantoms (with red, blue or grey glows)

• Hostile players invading with the Red Sign Soapstone, Cracked Red Eye Orb, Red Eye Orb, Blue Eye Orb, Cat Covenant Ring, Darkmoon Blade Covenant Ring, or Dragon Eye.
• Cannot be dismissed with the Black Separation Crystal, although they can quit your world using it.
• Enemies will disregard dark phantoms. In case of multiple invaders, dark phantoms can damage one another.
• In the case of the Soapstone, the summon sign is red. The Dragon Eye leaves a unique eye symbol that works much the same way.
• In all other cases, there is no summon sign; the invasion is initiated by your foe.
• Due to impassible fog-gates, Dark Phantoms can only leave your world via defeating the world host, being killed or otherwise defeated themselves, or using the Black Separation Crystal on themselves. (This largely leads to hosts choosing between fighting the dark phantom or hiding from them within the lock-in area.)