What you see
An "Achievement Earned" banner appears in gothic text at the top of the screen. Sparkles flash on it in some cases. In one case the player glowed yellow after looting a chest.

RELL Seas shows an "Achievement Earned" banner when you reach certain moments in play. The banner appeared after kills, boss hits and chest looting. The achievement names and rewards were not readable.
See the system breakdownNot confirmed yet: Type, How to use, World reference.
An "Achievement Earned" banner appears in gothic text at the top of the screen. Sparkles flash on it in some cases. In one case the player glowed yellow after looting a chest.
The banner showed after a kill in wave 1, in the middle of a fight with the Marines, and in the middle of the Aegon fight. It showed in the tutorial fight and when the finishing blow landed on Big Boss Man. It also showed when a hit on the beast took it to 56% damage, and during a stealth execute sequence.
During the stealth execute sequence, Gained Utility and Discovered Utility notifications appeared with the banner.
It is a banner shown at the top of the screen when an achievement is earned.
Banners showed after kills, boss fight hits, chest looting, the tutorial fight and a stealth execute. The exact triggers were not stated.
No reward was shown.
None was shown.