Requiem Mods and Requiem Relics are new additions to the game, introduced with Update 26, The Old Blood. They are the only thing that can kill your Kuva Lich, and they must be used in the correct combination on your Parazon to kill the Kuva Lich using a Mercy Finisher. While normal weapons and your teammates can damage her, the Lich will be weak for a certain mod combination, and only a hit with that combination can kill her.
To discover the combination, you must kill the Lich Thralls with the Parazon and collect Whispers. When you collect enough, once the suit mods will be revealed. You'll need to collect Whispers until you get to know all three, then experiment with the combination on the Lich until you get the right one.
Warframe - How to get Relics and Requiem Mods
Requiem Mods, listed below, are obtained from new Requiem Relics. These new Relics can be obtained from Kuva Flood as a guaranteed reward, as well as Kuva Siphons at a 50% drop rate. They also have a small chance to drop from Thrall's attacks, at 5%. They are then refined in the Void Fissure missions on Kuva Fortress. These are the only Relics that can be refined on Kuva Fortress, and they are the only Relics that can be opened in the Void Fissure missions that take place there.
Once refined, Requiem Relics will open and can drop a Requiem Mod for your Parazon. There are four types of Relics - I, II, III, and IV - which are displayed on a new screen in your Relic menu, which you can access from the Relic console in your Orbiter.
Requiem Relics can also drop an item called Riven Ribbon. These Riven Shards can be combined to create a full Riven.
Requiem Mods have limited payloads, with three each, and one is used when you kill a Kuva Lich with it. When all charges are used, the Mod can be broken down into Endo. You can also combine random and exhausted Requiem mods to create a new mod.
Lohk
We see smoldering gulfs
By what has no name
Error
His heralds are the stars he shoots down
Heaven and earth ignite
Flour
Bodily laws are not written
Like the suns and the retreat of love
Vome
To cosmic madness the laws submit
Although faithful spirits implore
Ris
In the bright space of blackened stars
They watch, accuse, deny
barrel
Growling, moaning, our kingdom
In the lost madness will die
Netra
The hordes of carrion make their laymen tremble
Agreement with eldritch plans
Khra
To the cosmic forms of tangent planes
We end like we started
