Before you enter
Select First Breach through the Dungeon/Breach Finder or its available portal. In online play, wait for the server to confirm entry before acting.
Decoder and Warden
Fight into the second room and interact at the cyan decoder relay. Continue to the Warden and secure the routing key. Read the objective HUD after each interaction, then follow the available extraction route.
Return to Harbor
Pick up useful drops and use the extraction portal. Wait for save confirmation in Harbor before launching the next activity. If you want a longer expedition once it is available, choose Three-Floor Breach.