Which event introduced Evo Shields before they joined Apex Legends' main game?

System Override introduced Evo Shields before they joined Apex Legends’ main game.

The limited-time event ran from March 3 to March 17, 2020, during Season 4. Its Deja Loot mode fixed loot locations and ring positions, while Evo Shields added a new progression system: players could strengthen their armor by dealing damage to enemy players.

Evo Shields were initially event-exclusive experimental equipment. Their success led Respawn to keep them in the standard game after System Override ended. They later became a major part of Apex’s armor system, eventually replacing conventional randomized body-shield progression in several forms.

A common mix-up is Lost Treasures, which later used Evo Shields in its Armed and Dangerous Evolved mode. Lost Treasures featured the mechanic, but System Override was the event that introduced it. War Games and Aftermarket were also later events, so neither is the original answer.