After Fireteam's successful escape from the Meridian Station, Cortana reunion with Blue Team in a strange Forerunner Map where they will discover the true reason for Guardian's activation. If Fireteam Osiris will feed the Guardian with the same coordinates they got from Meridian Station then it will take them to Sanghelios. Let's see how Blue Team and Cortana Manages to survive the Guardian in Mission 7: Reunion.
You'll again take control of Master Chief and led Blue Team to a Forerunner World. Now After the Cutscene goes straight ahead and activate the Forerunner device. As you activate the device it will take to and the team to a lower level.
Now head straight in the Genesis and take the right to find Cortana. Keep moving forward until you find some Grunts, take them down and use your D-pad and keep moving. Once you've entered the Forerunner Facility, take few more enemies and then climb up to activate another Forerunner device which will take you and the team underground.
Once your out of the Underground you'll notice another Guardian coming in, keep walking on the light bridge and another cutscene starts. After the cutscene, You need to keep moving into the tunnel listening to Warden Eternal's voice about Cortana. Get ready to deal with a bunch of enemies and keep moving ahead.
If you want to get rid of these enemies, check the tanned wall on the left-hand side which is probably the shorter route so just use your Spartan Charge to go through. Once you have dealt with all the Prometheans you'll come across Warden Eternal again for a Fight along with few more foes. You need to take continuous shots to damage him hard.
After a temporary Defeat of Warden, Cortana will contact you and gain you access to another light bridge to cross over and Enter a Big Building putting on a light show. Once your up, activate the final Forerunner device to take you lower level. Head straight and go across another light Bridge and keep moving towards another side towards the Gateway where Warden is sending more troops to stop you.
Keep Moving and Eliminate the troops on your way. You can either fly these Phantoms across the canyon or just take the footpath to reach across the other side. In the end, you'll come across the gateway where Cortana will guide you with the right path to the Gateway to the Forerunner Domain. The Cutscene will begin and end of Mission 7: Reunion. Once the currency is over you'll receive the achievement 'Together Again'.
