Bosses

Bosses
Corrupted Gundyr	Vordt of the Boreal Valley	Aborr	Curse-rotted Greatwood
Crystal Sage	Cathedral Guardian	Deacons of the Deep	Abyss Watchers
High Lord Wolnir	Old Demon King	Pontiff Sulyvahn	Aldrich, Devourer of Gods
The Lordran Remnants	The Fallen Protector and the Fair Maiden	Yhorm the Giant	Dancer of the Boreal Valley
Oceiros, the Consumed King	Champion Gundyr	Twisted Knight	Dragonslayer Armour
Ancient Wyvern	Trio of Explorers	The Nameless King	Mirror Knight
The Twin Princes	The Marauder	Soul of Cinder

Ashes of Ariandel Bosses

Bosses
Prince Dorthinus	Sister Friede	Princess Yngvil and Dearest Akseliane

The Ringed City Bosses

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

Minor Bosses

Minor Bosses
Carthus Sandworm	Demon	Stray Demon	Judicator Argo
Fallen Abomination

Curse of Attraction Extra Enemies

Extra Enemies
The Pensionist Horde	Abyss Watcher	Spirit of the Pontiff	Boreal Outrider Sentinel
Boreal Outrider Assassin

Summons

The possible summon signs usable for specific bosses.

Bosses	Possible Summons
Corrupted Gundyr	Sellsword Luet
Vordt of the Boreal Valley	Lion Knight Albert Sword Master
Aborr	Sellsword Luet
Curse-rotted Greatwood	Sellsword Luet
Crystal Sage	Eygon of Carim
Cathedral Guardian	None
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
The Lordran Remnants	None
The Fallen Protector and the Fair Maiden	None
Yhorm the Giant	None
Dancer of the Boreal Valley	Sword Master Lion Knight Albert
Oceiros, the Consumed King	Hawkwood the Deserter
Champion Gundyr	Sword Master
Twisted Knight	None
Dragonslayer Armour	Eygon of Carim Sirris of the Sunless Realms
Ancient Wyvern	None
Trio of Explorers	None
The Nameless King	None
Mirror Knight	None
The Twin Princes	Sirris of the Sunless Realms Orbeck of Vinheim
The Marauder	None
Soul of Cinder	Yuria of Londor Londor Pale Shade
Prince Dorthinus	None
Princess Yngvil and Dearest Akseliane	None
Sister Friede	Slave Knight Gael
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 2.15.