Ir Yût, the Deathsinger

"But what if what if what if, shhh listen, what if death were reified, described in its totality, made autonomous and universal, separate from any context or condition? What if She could invoke the ending of anything? How, then, would She know the song, and sing it, without Herself dying? [...] I am so terribly curious to know."

- Toland, the Shattered

Ir Yût, the Deathsinger is a Hive Wizard Deathsinger found in Crota's End. She is found in the final chamber of the Raid, and must be killed before Crota can be summoned.

First Crota Fireteam
"The charming Ir Yût made her introductions, and I was very pleased to meet her. We had a conversation, a little tête-à-Yût, a couple old wizards exchanging definitions. I defined myself a friend. She defined for me the quiddity of death, and she sang the song of that fearful autonomy."

- Toland, the Shattered

Encountering Ir Yût and hearing her Deathsong was the primary reason Toland, the Shattered joined the First Crota Fireteam on their quest for Crota. He had been quite interested in the Song for some time, trying to figure out how she could sing it without dying; he speculated that she made herself part of the song and became death incarnate. He did not hide his real goal from the fireteam members, openly talking about it with the fellow Warlock Eriana-3.

Toland did achieve his goal and met Ir Yût in the depths of the Hellmouth. It is unclear how their "tête-à-Yût" actually went, but it resulted in Toland being unsung from his biological form and banished, in some way, to the Sea of Screams. Ir Yût is also implied to have killed Eriana-3, as her designate is included on the file preserving the moment of Eriana's death recovered from Jax's remains.

Crota's End and The Taken King
"Bite deep, through reality, through the illusions of life and death, and eat what you find."

- Fang of Ir Yût (Adept)

Ir Yût resided in the Oversoul Throne, Crota's throne world, at the time of the Guardians' raid on the Hellmouth. She was slain by the Lightbearers, and armor and weapons were fashioned from the spoils. However, she could be found several months later attending Crota's death ceremony in the mission Last Rites, along with the Daughters of Oryx and few other Deathsingers. This points to her possibly being an Ascendant Hive, as well as still being alive somewhere, as killing her in the Oversoul Throne certainly wouldn't cause her final death.

Gameplay
Unlike all the other raid bosses before her, Ir Yût will not immediately be actively attacking any Guardians. Instead, she will have locked herself inside the room containing Crota's summoning crystal. At this time, all players should be focused on killing enemies, namely Shriekers. Once they are destroyed, she will activate her special ability.

Ir Yût is an especially dangerous wizard, as her special power is the Deathsong, which kills anyone who hears it when it is complete. She will start the song once any Guardians are detected, in which they will have three minutes to kill her before she completes it. There will be a countdown for the last 30 seconds of this song, which is when the barrier will be unlocked, allowing the player to unleash all damage on her as possible.

Challenge Mode
Age of Triumph added a Challenge Mode for Ir Yût. In order to complete it, the players must kill everything in the area (including the Wizards and Shriekers) and then kill her with an Ascendant Sword. Once the first wave of enemies are killed, a message saying "Ir Yût shrieks in fear" will appear on the bottom left. The fireteam must rush into the open area and kill everything (including Ogres) once more to spawn a Swordbearer. Once it is killed, a Guardian must pick up the sword and rush back to Ir Yût and kill her with one swipe.

Trivia

 * Because she belongs to the Spawn of Crota, Ir Yût may be a daughter of Crota, or a relative.
 * She is mentioned in the book Lore:Inquisition of the Damned as one Crota's most cherished courtiers, and remarked upon having long given up on rebuilding the mythical Choir of Deathsingers - something Azavath dreamed of and later achieved.
 * Ir Yût is also a character in Calus' prophetic stories, where the Shadows recover her essence from the Ascendant realm, learn the Deathsong from her, and reverse it in order to bring Toland back to life. Underscribe Shipal is, however, criticised by other scribes for inaccuracies, paradoxes and misinterpreting Hive sources in this account.