Bosses

Bosses
Vordt of the Boreal Valley	Curse-rotted Greatwood	Crystal Sage	Deacons of the Deep
Corrupted Gundyr	Abyss Watchers	High Lord Wolnir	Old Demon King
Pontiff Sulyvahn	Aldrich, Devourer of Gods	Yhorm the Giant	Dancer of the Boreal Valley
Oceiros, the Consumed King	Champion Gundyr	Dragonslayer Armour	Ancient Wyvern
The Nameless King	The Twin Princes	Soul of Cinder

Ashes of Ariandel Bosses

Bosses
Sister Friede	The Triad

The Ringed City Bosses

Bosses
The Demon Prince	Darkeater Midir	Slave Knight Gael	Halflight, Spear of the Church

Minor Bosses

Bosses
Carthus Sandworm	Demon	Stray Demon	Judicator Argo

Summons

The possible summon signs usable for specific bosses.

Bosses	Possible Summons
Iudex Gundyr	None
Vordt of the Boreal Valley	Lion Knight Albert Sword Master
Curse-rotted Greatwood	None
Crystal Sage	Eygon of Carim
Deacons of the Deep	Anri of Astora Horace the Hushed Sirris of the Sunless Realms
Abyss Watchers	Sirris of the Sunless Realms Yellowfinger Heysel Black Hand Gotthard Londor Pale Shade
High Lord Wolnir	None
Old Demon King	Great Swamp Cuculus Knight Slayer Tsorig
Pontiff Sulyvahn	Anri of Astora Black Hand Gotthard Londor Pale Shade
Aldrich, Devourer of Gods	None
Yhorm the Giant	None
Dancer of the Boreal Valley	Sword Master
Oceiros, the Consumed King	Hawkwood the Deserter
Champion Gundyr	Sword Master
Dragonslayer Armour	Eygon of Carim Sirris of the Sunless Realms
Ancient Wyvern	None
The Nameless King	None
The Twin Princes	Sirris of the Sunless Realms Orbeck of Vinheim
Soul of Cinder	Yuria of Londor Londor Pale Shade
Sister Friede	Slave Knight Gael
The Triad	None
The Demon Prince	Slave Knight Gael Amnesiac Lapp
Darkeater Midir	Shira, Knight of Filianore
Slave Knight Gael	None
Halflight, Spear of the Church	Unbreakable Patches

Information here is accurate for version 1.67.