Resonant Knife

The Resonant Knife, First of the Reshaped (originally Keit'Ehr) is a Taken Subjugator and Dread leader who commands the Dire Taken on the Dreadnaught. The Witness made it from Light and Resonant Darkness, but it was abandoned as a failure before waking and being Taken by a new voice.

Kludge

In Kludge, the third mission of Episode: Heresy, the Resonant Knife confronts the Guardian at the portal frame in the Hall of Souls. It is listed as the mission's boss, but the Guardian is meant to evade it and flee to the Trenchway rather than fight it.

Resile

In Resile it guards a Taken force field at the Hull Breach and summons Dire Taken. Its shield can be broken with Willbreaker. It returns with two Channelers of Terror in the Mausoleum and is finally slain in the closing encounter.

Lore

It ambushed Eris Morn and the Drifter in the Court of Oryx, killing Eris. The wiki notes that Eris was later revealed to be alive.