The Moonlight laser blade is a recurring weapon in the Armored Core series, and has also appeared in other FromSoftware games in the form of the Moonlight Greatsword. The ridiculously powerful melee weapons is definitely here in Armored Core VI Fires Of Rubicon.
The IA-CO1W2: MOONLIGHT isn’t unlocked normally via progress. Rather you must find a part container to unlock it.
To find the Moonlight laser blade, you need to reach the mission “Investigate The Coral Coral Convergence” that concludes Chapter 4. After the first encounter with two ACs, you should be heading to a bridge. Follow the bridge and then fall down below where it ends. There should be a chest surrounded by a number of enemies all with battle logs if you defeat them.
All you need to after that is complete the mission. Good luck with that boss fight down the crater.
The Moonlight laser blade in AC VI is technically a combination of a Pulse Blade and a Laser Blade: A Light Wave Blade. It’s the only melee weapon that emits a projectile, which can be comboed twice to produce an X slash. Charging the Moonlight down and it will unload a devastating energy attack with a huge arc and range. The downside is that cooldown times is ridiculously long.
AC VI has a several other secret parts found from part containers or through collecting enough battle logs.
You can find our review of Armored Core VI Fires Of Rubicon here.