The Balor Fomorian is an event produced by Vay Hek to assault a Relay. Here is how to participate:
1.) Get some Omega Isotopes - These are a random enemy drop from any mission on the planet with the relay the Fomorian is attacking.
2.) Craft the Fomorian Disruptor and equip it via Gearwheel in your arsenal.
3.) Start the mission.
4.) Fly towards the ship and destroy Zeplens if they trap you. Destroy the two shield generators which are waypointed.
5.) Fly into the Fomorian ship.
6.) Activate the Disruptor via Gearwheel once your squad is present. (Game warns you if not all players are close enough, but this can be ignored my selecting it from the Gearwheel again)
7.) Shoot all available Fomorian Cores, which are visible as cylinders capped with a yellow circle. Continue to shoot the Fomorian until the timer expires if all cores have been destroyed, as this yields a higher points score for the mission.
9.) Exit the ship and go to a safe distance. You will be extracted automatically.
The event rewards 200,000 Credits and an Orokin Catalyst upon successfully doing 1 million damage as a squad. Here are the Drop Tables for extra rewards, such as the Imperator Vandal.