Krosis

Krosis is one of the eight Dragon Priests. His name means "sorrow" or "pity" in dragon language.

Interactions
Krosis can be encountered at the Dragon Lair of Shearpoint in the company of a leveled dragon.

He emerges from his sarcophagus located directly in front of the Word Wall once approached. Krosis is a frost-based dragon priest, however he is often mistaken for a fire-based type, due to his tendency for using his Staff of Fireballs.

Krosis is one of the two unique dragon priest not contained in a building, the other being Nahkriin. He also wields a Staff of Fireballs. This makes the encounter with Krosis more challenging than the fights against the other unique dragon priests.

Notable items
Upon his defeat, Krosis drops the Krosis Mask - one of the eight mysterious Dragon Masks located throughout Skyrim. Collecting all eight masks is a requirement to restore the Dragon Priest Shrine.

The word wall guarded by Krosis contains all 3 parts of the shout Throw Voice.

Trivia

 * Draugr will occasionally say "Unslaad Krosis", which means "Eternal Sorrow" in the dragon tongue.
 * When Paarthurnax, Odahviing and Tamed Dragons engage in discussion with the Dragonborn, they tend to say "Krosis" as the human word "pardon". Krosis is usually used in this way when the Dragonborn does not fully understand the subject area of what the Dragon says.
 * Because dragon priests have a natural tendency to float backwards away from their attackers or otherwise strafe to maintain a healthy distance, Krosis is known to sometimes float off the northern cliff of Shearpoint if attacked from any direction other than north.
 * Page 195 of the Skyrim Official Game guide, it says that Krosis is at Kilkreath Ruins  while he is actually at Shearpoint.

Bugs

 * Sometimes if you get close to Krosis fast enough when he gets out of its coffin, there's a chance that Krosis won't attack you at all (assuming you maintain the same distance).
 * Killing the dragon before facing Krosis, and then hiding behind the dragons skeleton may cause Krosis to float back and forth aimlessly, allowing you to shoot him with arrows without being attacked by him. Using a shout on him seems to "reactivate" him, though.
 * Because Krosis can deal a significant amount of damage, the player might find it useful to hide behind the stone ruins Southwest of the Word Wall. This does not "deactivate" Krosis, as he will still use magic attacks, but it is easier to pelt him with arrows, as he usually does not advance towards the player. Krosis will still move left or right to avoid being hit.
 * Sometimes, if you use the Unrelenting Force shout, or finish Krosis off with an arrow, he may become trapped in amongst the rocks on the cliff, making it impossible for you to loot his body and retrieve the mask.
 * Leaving the Dragonstone and coming back (without acquiring the mask) will make the ash pile of Krosis disappear, making the mask of Krosis unavailable. The armor/skeleton however should still be present, and possible to loot.
 * After killing the Dragon sometimes Krosis doesn't come out of his tomb at all. There is currently no known way to fix this bug.
 * Sometimes after defeating Krosis, his body might disappear making it impossible to loot any of his items.
 * Sometimes after defeating Krosis, it is possible to pick up his staff lying on the ground, and then acquire a second staff from his ashes. Both have the same stats, making it possible to sell one while keeping the other. There are no known circumstances that have to be met for this to happen; it has been completely coincidental.

Gallery
Кросис (Жрец)