Fort Condor is one of the major mini games located in Chapter 4 in the Junon region. While optional you do need to complete all four levels to get the protorelic for the region.
The game itself is a basic tower defense style game where you need to drop the right units down to counter the enemy. Every level of Fort Condor is fixed and it largely comes down to trial and error until you find the correct timing and placement.
If you find this process tedious and just want to move on with your life, here is no commentary guide on how to beat every Fort Condor level for you to follow along. Use the timestamps as needed.
00:00 - Intro
00:34 - Level 1
05:12 - Level 2
08:58 - Level 3
11:45 - Level 4