Annihilation is a weekly challenge mode where you face endless waves of enemies on a large map. The goal is to defeat as many enemies as possible, up to a certain cap (usually 400), to earn Orundum. Orundum is the premium currency used for operator recruitment (gacha pulls), making Annihilation a vital weekly activity.
There are typically multiple Annihilation maps available, rotating periodically. Each map has unique enemy compositions and layouts. It's recommended to clear each Annihilation map once manually to understand the enemy waves and optimal deployment strategy, then use the 'Auto Deploy' function for subsequent runs. Aim to reach the 400-kill mark on at least one Annihilation map each week to maximize your Orundum income. A stable auto-deploy team for Annihilation is a significant milestone in your progression.