Warframe: SILENCE VAY HEK

Tenno,

Councilor Vay Hek is vulnerable. The failure of Project Tethra was so devastating that he has been forced into hiding. This is our chance -- find Hek and take him out.
Hek has consolidated his remaining shipbuilding on Ceres. To protect the operation, he's sent in his personal guardsmen, deadly Prosecutor class fighters. Ever paranoid, Hek has each Prosecutor carry a locator beacon so he can track them at all times. His paranoia will be his undoing. Collect enough locator beacons and you can use this Frequency Triangulator to determine his whereabouts.
Do not assume this will be easy. Not only are the Prosecutors viscous melee fighters but intel shows their auras create a new type of shield barrier, impervious to most types of damage. Getting through those shields will be difficult. You will need to experiment to find their weaknesses.
Go to Ceres, defeat the Prosecutors to locate Vay Hek, and then take the fight to his doorstep.

-The Lotus
HERE'S WHAT YOU'LL NEED TO DO

- You will receive an in-game message from the Lotus that includes a Frequency Triangulator. This gift will be essential in locating Councilor Vay Hek.

- Visit the Shipyards on Ceres. Here you must Defeat Councilor Vay Hek's Prosecutors. Beware, Tenno! They are unlike any enemy you have fought before. Each Prosecutor is vulnerable to a primary elemental type (fire, ice, toxin or electrical damage) and you must use this to your advantage. For greater success, team up with other Tenno using multiple elemental types.

- Some of the Prosecutors carry coordinator fragments that will drop once you have defeated them. There are four fragments: Frequency Delta, Frequency Gamma, Frequency Kappa and Frequency Omega. You'll need a certain number of each to use in conjunction with the Frequency Triangulator. This will help you determine Vay Hek's location.

- Find Vay Hek and take him down!

Successfully defeat Councilor Vay Hek and complete the mission to receive one of these rewards:
- Hydroid Helmet Blueprint
- Hydroid Chassis Blueprint
- Hydroid Systems Blueprint