Midnight Guard
From the MEGA Wiki
The Midnight Guard is an outfit cosmetic for your Titan. It's unlocked by the Titan Tussle achievement: Win your first kaiju duel.
Equipping
In the lobby, pick a Titan and click Customize, then find the Midnight Guard under Outfits and click Equip Item. Each Titan keeps its own look, so it has to be equipped per Titan. Until it's unlocked it can be previewed but not equipped.
Other outfits
Cosmetics
Unlocking
City Cap
Frontier Titan
Builder's Hard Hat
Iron Chef
Party Animal
Neighbourhood Beanie
High Society
Monarch
Titan Shades
Champion Shades