The Grustrag Three is an elite squad of bloodthirsty Grineer used by Councillor Vay Hek to punish Tenno who side with the Corpus in the ongoing struggle for dominance over the Origin System. Fighting alongside the Corpus against the Grineer in an invasion mission five times in a row will trigger a death mark against the Tenno, and they will receive an inbox message from Vay Hek warning them.
Interfering with our operations is unacceptable. You will be shown your place. Your punishment has been ordered.
—Councillor Vay Hek
Subsequent death marks will have a different inbox message:
You continue to assist our enemies. Your meddling will NOT be tolerated.
—Councillor Vay Hek
Once the Tenno has received a death mark, the Grustrag Three can appear during any mission against the Grineer. During the course of the mission, the screen will flicker and the Lotus will send garbled transmissions.
Lotus: "Tenno, stand… something is happening."
Lotus: "These readings— this should not be possible. Tenno, my sensors are…."
Lotus: "The… has been designed… fight and kill Tenno… do not risk…."
Lotus: "Get away now. You don't want…."
Lotus: "Tenno, listen carefully: you are being hunted by…. Abort the mission… get to extraction…."
After the third transmission from the Lotus, any remaining mission objective will vanish and extraction will be marked, but the Grustrag Three will spawn shortly and lock down the map. All three have different, powerful weapons, and each also has a Carabus sentinel following them around. If they manage to down a Tenno, one of the Carabi will hover over the Tenno, projecting a shield around them that prevents other Tenno from reviving them. While the Tenno is bleeding out, the Carabus will attach a Grustrag Bolt to the warframe. If the Grustrag Three manage to attach a Bolt to their intended target, the mission will automatically fail for all Tenno.
Each of the Grustrag Three have their own dialogue lines during combat.
"YYYou are the sc-crawniest of them all!"
"Are you the b-b-best they have!?"
"SSShiny little p-p-pretty things, you Tenno are!"
(after an ally is killed) "U-u-unacceptable!"
(while capturing a Tenno, variant) "Starting capture."
(while capturing a Tenno, variant) "This one is mine."
"I want to play with these ones."
"[playername], your [warframe] looks so… slippery."
(after an ally is killed) "You are going to suffer for that, Tenno!"
(while capturing a Tenno, variant) "Wait til you see what comes next!"
(while capturing a Tenno, variant) "Did you know this is my favourite part?
"Are we sure these are the targets? They seem so inconsequential."
"Do not waste my time, Tenno!"
"You are beneath us!"
"One of them is wearing a scarf!"
(after an ally is killed) "That one will be difficult to replace."
(while capturing a Tenno, variant) "Too easy."
(while capturing a Tenno, variant) "Pathetic."
If the Tenno squad manages to kill all three, the Lotus will come back online.
(variant) Lotus: "The Grustrag Three have been eliminated. Impressive, Tenno, but next time, follow my orders."
(variant) Lotus: "That was the last of the Grustrag Three. You took a risk, but it paid off."
(variant) Lotus: "The mission was scrapped, but everyone made it out. That's what matters."
The lockdown will be lifted if still in effect, and extraction will be marked (as any outstanding objectives were cleared when the Grustrag Three arrived).
If the Grustrag Three managed to defeat the Tenno, the mission will fail and the Tenno will return to the Orbiter. The Grustrag Bolt will be attached to their warframe, replacing the right shoulder emblem with a badge that reads "PROPERTY OF GRINEER". As long as the Grustrag Bolt is attached, that warframe's damage against the Grineer in subsequent missions will be reduced by 50%. The Lotus will send an inbox message containing a blueprint for a Grustrag Bolt Release.
The Grineer have attached a corruption device called the Grustrag Bolt to your warframe. It will cripple your powers when you attempt to fight against them. However, you can remove the device by crafting the attached blueprint. Good luck.
The Bolt Release costs 5.000 cr, 1 morphics, 1 neurodes, 1 neural sensor, and 20 oxium to build, and takes 1 minute. Upon claiming it from the Foundry, it will immediately be applied, removing the Grustrag Bolt.
The Grustrag Three also appear in the quest A Man of Few Words, the Law of Retribution Trial, and the Pyrus Project. They are mentioned by a Grineer captain overheard on the Radio Scanner, and their background is revealed in their Codex entries.