"Loot chests" refers to containers or boxes found in video games that contain valuable items or rewards that players can collect or use to progress in the game. Full definition
Now you only get bonuses if you use «mods» obtained from loot chests that you need to spend credits on and presumably real money in the future. (microsoft.com)
These playable spaces will be larger than those found in Destiny 1 and include more secrets to uncover, including caves filled with loot chests and bosses which hold the key. (eurogamer.net)
For instance, the animation of a rare loot chest opening looks very fluid and realistic. (gamingenthusiast.net)