Undead Siege is a Zombies mode featured in Call of Duty: Mobile. The mode was originally released on August 1st, 2021 as part of Season 6: The Heat update before being removed on September 23rd, 2021 with Season 8: 2nd Anniversary. The mode returned on October 20th, 2021 as part of Season 9: Nightmares and was removed on November 16th, 2021 with Season 10: Shadows Return.
Undead Siege is based on the "Seven Days of Siege" mode from Call of Duty: Online with elements of the Outbreak mode from Call of Duty: Black Ops Cold War, Undead Siege was released on August 1st, 2021 as part of Season 6: The Heat update.
Taking place on a section of the Isolated map from the Battle Royale mode, Undead Siege features several enemies, objectives to complete and rewards to unlock. The mode also takes elements from the Treyarch series of Zombies by primarily featuring items such as Perk-a-Cola machines alongside the wooden Mystery Box.
A game of Undead Siege consists of day and night system, and both phases last a few minutes. During the day, the players can explore and collect loot for the upcoming night. When there are 20 seconds left in the day, the player will be automatically teleported back to the "teleportation base," so wandering too far is not a worry.
On Hard Mode, after the third and fourth night, players will be able to complete side missions. There are multiple side missions, which are:
- Escorting Dempsey as he drives a truck full of Aether Crystals, and preventing any zombies from getting in close proximity
- Destroying an Infection Source, which is a giant Aether Crystal
- Killing the Butcher Boss from the standard Battle Royale.
Missions can only be accepted with a limited time frame, but are reasonably close to the base, about 200 meters away. Side missions, when completed, reward a large amount of loot, including ammunition, turret materials, and weapons. If side missions are failed (by not completing the objective in time), they will spawn smaller amounts of loot, and said loot will usually not be as valuable as a completed mission's loot.
Defending the Base
During the night, a specified area around the teleportation base will be safe from the surrounding radiation storm, stepping out into said storm for too long will eventually kill the player (health decay in the storm at the rate of 10/sec). During this time, players can use the loot they've acquired to build turrets than can assist in eliminating zombie threats, and said turrets can be modified and upgraded up to four times. Players can also buy items from the base like ammo, a Death Machine, and custom weapons similar to Battle Royale.
Depending on difficulty, the game will last for 3 days and nights on Casual mode and for 5 on Hard mode. In Hard mode, players will encounter specialized zombies much sooner and in greater numbers, thus necessitating strategy and careful usage of turrets to win. The game ends when the player has survived all nights, or the base is destroyed.
Mystery Boxes do exist, and players can usually find a Perk-A-Cola near them. The cola that will appear near the Mystery Box can be randomized in some locations. Mystery boxes can usually be found in a similar fashion to normal zombies, as a giant blue beam will mark their position. With Season 9, the Mystery Boxes and Perk-A-Colas were moved to be right by the base, so when players have returned to the base after looting for the day, they can grab some items for the road ahead.
The player has a wrench by default that can heal damage from both the base and turrets erected by themselves or teammates.
At the end of each match, players will be awarded with varying drops depending on the mode, though there is a chance player may not get a reward, such as when you leave the game. If players leave the game, they will receive a portion of the EXP towards their Battle Pass, but have a high chance of not getting any reward drops.
Talents are a unique feature that upgrade various aspects, including:
- Turret damage
- Turret endurance
- Weapon damage
- Player health
- Wrench damage.
When a talent has been fully upgraded, a special ability will be unlocked, ranging from a magazine increase to a movement speed increase. All upgrades however will require Aether materials, but that can be obtained in normal gameplay or through the Richtofen's Rewards system.
Five talents have been added with Season 9, though none of them are unlockable as of current.
Completing various challenges will earn XP for Richtofen's Rewards. It has 50 tiers and consists of both camos, Aether materials, an epic skin and an epic blueprint.
The map of the game mode is a modified version of Isolated, which has a smaller play zone and features Infected Areas, which usually contain more loot, including a Mystery Box and Perk-A-Cola, as well as more zombies.
The mode has one easter egg which involves the players accessing various computers with varied passwords. After unlocking a computer, they will unlock an entry concerning various zombie types. They will also be rewarded with some turret materials.
Computers can be found in:
- Sakura - Inside of a dark red house, which is near the center of the area, on the bottom floor. The password is 0418
- Outpost - Inside of a faded green house, second house north from the water on the left side. Also found on the bottom floor. The password is 6682
- Nuclear Plant - Inside the building south of the reactor on the west side, and on the bottom floor. The password is 7529
- Sanitarium - Inside on the bottom floor on the Help Desk. The password is 4689
Undead Siege also features comics, similar to that of the normal Battle Pass, except these focus after Tank Dempsey's funeral. After his funeral, the Primis crew lament his loss, and due to them being unable to progress without him, they begin to seek out another Dempsey to replace him, who ends up difficult to find alive and difficult to keep alive.
When they finally are able to recruit a Dempsey, he is in disbelief of what the Primis group has told him, and Richtofen attempts to prove it using the Summoning Key. However, it fails, and the Primis group is surrounded from zombies.
The player controls Seraph (referred to as Alice, in reference to Alice in Wonderland, by the Primis group), who has been sent into a section of the Battle Royale map, Isolated, which has been corrupted by the Aether, and is about to be shot before Primis Richtofen confronts the player. He gives them a choice, to help the Primis crew or die. The player chooses the former, and over time, learns that due to Takeo being injured, the crew is overwhelmed, and that Richtofen is doing his best to get back to their "home," though what this refers to is unknown. Although the general plot is the same, helping the Primis Crew escape with their teleporter, depending on mode there can be extra dialogue, usually in Hard Mode rather than Casual Mode.
In Hard Mode, it is stated by Richtofen during the third and fourth nights that something or someone may be keeping the Primis group inside of Isolated. However, this is not explored further as Richtofen and the others are presumed to have escaped after the fifth night.
- In a beta test server for Season 8, the Zombies mode button (where players launched Undead Siege) was named 7days, though it was not accessible.