Mercy kills in Warframe allow you to instantly assassinate a target who has dropped to five percent of their health. If you have a build that utilizes impact damage, it can increase the chances of being able to perform a mercy kill at a higher percentage of their health by ten percent for each stack of Impact damage.
You will know when you can perform a mercy kill because a red symbol, shown in the image above, will appear above the head of the enemy. You can then interact with them using the prompted on-screen button to perform the mercy kill. Mercy kills have drawn out animations, much longer than the average finisher.
Mercy kills are performed with your Parazon, a Tenno multitool that all Warframes wear on their wrist. The Parazon can also be used for hacking, killing Kuva Liches, and Kuva Thralls or Larvlings. Any of these kills, except the Kuva Lich, will count as a Mercy Kill for the sake of a Nightwave challenge.
The reason to perform mercy kills instead of finishers boils down to the mods that you can equip on your Parazon. Performing mercy kills with certain mods attached will leave to statistical and gameplay benefits that you do not get from finishers.
These mods can be found by killing bosses and will give you the below benefits.
- Blood for Life: 50% chance to create a Health Orb on Mercy.
- Blood for Energy: 50% chance to create an Energy Orb on Mercy.
- Blood for Ammo: Mercy refills magazine by 100%
- Hit and Rune: On Mercy: +60% Parkour speed for 6 seconds
- Out Of Sight: Blind Enemies with 18 meters on ‘Mercy’ kill.