Strike missions are not a part of the main story in Destiny, these are individual missions which are a bit harder than the actual story. Earth Strike mission, The Devil's Lair can be started at the eighth level. You will face Fallen and Hive enemy factions in this mission.
From outside the Refinery, you will be asked to enter The Devil’s Lair through the Rocketyard. This strike mission can be completed with the help of two more players, that is a fireteam of 3 players.
There will be a huge number of Hive Acolytes and Knights in this mission. Go through hallways in the Refinery and reach the fight between Hive and Fallen. You can wait for them to finish each other or take part in the battle for extra experience and kill the last enemy. There will be many battles going on between Hive and Fallen. Try to kill them from behind, you will be more successful.
After killing them, deploy Ghost to the Mesh generator and hack it. This will help you advance in the game.
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