The Borg Ground Invasion happens on the planet Defera on specific times on specific dates. Check the calender for the times. Brandon (PWE_BranFlakes) will occasionally put together a ground event, where captains will come together and group up. Check the forums or the REDALERT chat channel for details. It'll usually happen for the first hour of the event. Note that unlike STFs, Klingon and Federation players cannot group together.
The Borg Ground Invasion happens for two hours (Occasionally 4 hours on weekends when indicated). That means you have two hours to complete everything you want or farm as much Borg samples as you can. Once the time limit is reached, everyone will be returned to base camp, and the Borg will disappear back into the Probe. You're missions will be dropped. This means you'll have to do all the missions over from scratch each time the invasion occurs.
The Invasion is separated into five different locales on the same map. Base Camp is the hub where everyone beams in at the start. From here you get the quests for the other four locations. There's a crafting vendor with special items for crafting that are specially tailored to fighting the Borg. You'll need to collect Borg components from dead Borg to craft them. There's also a mail console at the back. You could potentially walk to each of the other four locations from Base Camp. The easiest way however, is to jump into the action by taking the transporter pads.
Each location (except the Probe) has Easy, Medium, and Hard Missions. You have to first complete ONE easy mission to unlock the medium missions, and ONE medium mission to unlock the hard mission. After completing one hard mission for either City, Temple, or Power Plant, you'll unlock the Hard mission for the Sphere.
A note on Sharing missions. It's possible to share missions, for instance sharing a hard with someone who has to finish medium first. If they accept, they won't be able to turn in the mission. If you want to get credit for doing the mission, you first have to complete a medium mission, turn it in, then accept the shared mission. Otherwise it will count as a secondary even if you've completed a medium after accepting, and won't be able to claim the reward.
EXTREMELY BIG IMPORTANT REMINDER: Bring a remodulator to this instance. You can craft a better one at the crafting station, but the Borg can and will adapt to your weapons. This will make it especially difficult fighting any Borg, since you can't do much damage against them when they've adapted. Remodulators can be gotten through your Replicator in space. They're at the top of the list, and they're free. If you don't have one, try asking around for one in Zone, sometimes generous people have spare remodulators to hand out. You can get ONE remodulator at the start by telling the Base Camp commander you don't have a remodulator.
The city is accessible by either walking through the main gate or taking the transporter on the left side of the Holomap table. This is a good place to start to familiarize yourself with the structure of the Invasion Event.
Help the Deferi defense force by uploading software to their Phaser defense turrets. They're scattered all across the City area, the majority are close to the main gate of the Base Camp.
If the turret has a Deferi appearing to work on the turret, then it needs to be remodulated. If the turret has a Deferi standing and pointing defiantly at the Borg, it has already been remodulated. The turrets get adapted to 2 minutes after someone remodulates them.
Just upload the software through an interact, and when the turret remodulates the mission will +1. A total of 10 turrets must be remodulated to complete this mission.
Gain insight into what the Borg are planning by collecting Drone Cortical Arrays. Cortical Arrays will randomly drop from defeated drones. They don't interfere with other drops, so you'll get them in addition to any loot you may get during this mission. Collect 50 to complete this mission.
These are relatively easy compared to the other two Medium sets. You don't have to necessarily team with others, but it does help.
Go door to door and evacuate any Deferi who are trapped in their homes. The Deferi homes are located at the center of the City area. Two Tactical Borg drones will be attempting to break down the door. Eliminate them and knock on the door. There occasionally will be no one home. Collect 15 civilians to complete this mission.
The Borg are attempting to assimilate the Deferi Civilians. Each victim will be surrounded by Drones attempting to assimilate them. You must eliminate all four to claim the Civilian. There's a progress bar that appears above the victim, you have until that bar completes to save the victim. If you fail, you will have to contend with the workers as well as the newly assimilated drone. You can eliminate three of the drones and push the last one far away to delay the timer, but it's difficult to pull off. Collect 15 civilians to complete this mission. (Everyone on the team will get credit as long as they're close when the drones are killed).
You must be in a team of at least 3 people for this mission to start.
Knowledge is Key
This has bugged for me and several other people numerous times, though I've seen people complete it. Basically you upload a virus, and interact with the spasming non-assimilated (no Borg components on them) Deferi. After that you'll have to do something with the partially assimilated Deferi. Finally, you'll have to kill all the fully-assimilated Deferi to complete. I believe this has a chance to drop the Borg Tactical Armature. I'll update this when I actually have a chance to complete this.
The power plant transporter is located behind the Holomap projector at Base Camp. Take this, because it's way too far to walk. If you're in the city and too far from the transporter, the Power Plant is to the west of the City.
The Borg have done something to the Coolant tanks of the plant. Defeat the two drones surrounding the tanks to gain access to them. Interact with the tank to seal it off. It takes 2 minutes for the Borg to beam back in and start another coolant leak. The coolant tanks are located mainly at the corners of the corridor and at the ends. 10 Coolant leaks must be sealed to complete this mission.
The Borg are attempting to divert the power generated by the plant to their Probe. Stop them by cutting off their access at each of the Control stations. You have to interact with two consoles at each station. The consoles are guarded by numerous Borg drones. When you interact with one of the consoles, two Borg drones will beam in behind you to stop you. Defeat the drones if they interrupt you to successfully interact. If you're in a team, have one person interact with the console while the others cover them.
It's strongly recommended that you be in a team of 3 or more to successfully complete these.
Engineers have trapped themselves behind forcefields to keep out the encroaching Tactical Drones attempting to assimilate them. Clear the area and get the Engineers out from the forcefields. There are four chambers with engineers, each in the outer areas of the map. Go through the side doors of the the alcove chambers to reach these chambers. There will be three Tactical Drones who are guarding the Engineer. After they've been defeated, signal the Engineer to lower the force field. 15 Engineers must be rescued to complete this mission.
The Borg have established alcoves in the lower levels of the Power Plant. They're leeching power from the plant to regenerate their drones. To deactivate the alcoves, you'll need node keys which the regenerating Borg drop. You need a total of 5 node keys to shut off 1 alcove group. Have one person collect the node keys so that they can shut off the alcove group. 10 Alcoves must be deactivated to complete this mission.
You must be in a group of at least 3 players to begin this mission.
Getting to the Bottom of Things
The objective here is to hold off the Borg who have made this area their base. You'll have to beat down the Elite Tactical that comes out of the main Forcefield, then defeat the surrounding Drones. After defeating the Drones, Heavy Tactical drones will appear. After the Heavy Tactical drones are defeated, the Elite will make one last stand. After defeating the Elite, take the loot bag that drops behind the console that triggers the mission to claim the Power Plant Access Codes. These codes are what you use to turn the mission in.
To reach the temple, use the transporter at the right of the Holomap projector at base camp.
The Borg are making an offensive against the Archeological camp. You'll need to use Antiproton turrets to lower the Borg's shields and eliminate them. The Antiproton turrets can be set up in the glowing outline. Once deployed, you'll have to attack a Borg Drone or group of Drones for the turret to start attacking them. Deploy 10 Turrets and defeat 12 Borg Drones to complete the mission.
Preservation of Knowledge
The collected Preserved Artifacts must be evacuated to the appropriate facilities. Collect information on the items to be moved and make the appropriate arrangements. Then modify the transporter to transfer the artifacts. The minigame is mostly a switching game where you have to swap out chip parts to complete. You must successfully answer the trivia questions (read the description carefully, the answers are easy to spot in there) 12 times, and complete the chip minigame 12 times to complete this mission.
You may want to have a team of 2 or more to complete these missions, if only to res you in the trenches.
The Borg have assimilated the temple's priests. Save them by defeating them and beaming them out. They usually roam in pairs around specific areas. Be careful, they behave like Tactical drones and fire burst plasma bolts which can take a huge chunk of health. Once you've dropped their health, they'll turn friendly and you'll be able to beam them out. You must rescue 30 Deferri Priests to complete the mission.
What's Mine is Mine
Tag the exposed Preserver artifacts for beam out. You'll have to clear the nearby Borg drones from the artifact before being able to beam it out. Be careful, some unscrupulous people will wait for you to clear the area and swoop in and steal your artifact while the Borg are distracted. You must tag 30 artifacts to complete this mission.
This mission requires at least 3 players to begin.
The Borg are attempting to take the Temple. Stop them at all costs. The Borg will beam in waves, protected by a Borg Repulsion Dome. As you deal with each wave, the Borg will push you up the temple's floors. When you've cleared the top portion of the temple, the mission is complete. Note that if 10 drones reach the top of the Temple, or if everyone dies, the mission will fail.
You must be in a team of at least 3 people to begin this mission.
This mission has you going near the heart of the Borg invasion force and defeating an Assimilated Gorn. (This is not as hard as it sounds). There is no transporter to the Sphere, you'll have to walk through the borgified trenches to the North of base camp to reach one of the a pillar consoles to summon one of the 12 Gorn Borg. You need to be in a team of at least three people to do so.
Once summoned, the Gorn will beam in close to the Console, but not directly near it (maybe ~10 m, so don't directly face the console or you'll get massively flanked). The Gorn will beam in with a small detachment of Tactical Drones for back up, but your primary concern should be the Gorn, as he has a Mortar on his bank that hurts. If you're at close range, he'll use standard Borg melee tactics, in addition to attempting to bite you. Once you've defeated him, return to base camp and retrieve your reward.
Also note that there is an accolade for defeating all 12 Gorn. If you're dead when the Gorn is defeated, you won't get credit for the kill. Vis-a-Vis, keep your team mates alive and res them when their down if you can.