| SSS | Missions | Rewards | Guide | Trivia |
Stationary Security Service (SSS or S3) is a game mode in Arknights. It is accessible from the Terminal since the Lingering Echoes update once 1-5 is cleared and after the player have unlocked an Operator Module.
Overview[]
S3's gameplay is reminiscent to deck building card games such as Magic: The Gathering and Yu-Gi-Oh! in which players have to build a "deck" of Operators and clear sequential operations with them.
Playing S3 is needed if one wants to upgrade Operator Modules, as 
Data Supplement Stick and 
Data Supplement Instrument – the materials to do so, are primarily obtained here.
To play S3, the player must select a Security Mission, then choose the Directional EC Unit and Tactical Equipment for each class (explained below), and assign Operators to the squad, and finally start the mission. Like Contingency Contract and Integrated Strategies, S3 does not consume the player's 
Sanity to run.
After clearing a Security Mission added from the second rework for the first time, its Emergency Resupply mode will be unlocked. Playing in this mode doubles the rewards but applies a handicap, increases the initial Danger Level of each operation, and causes the player to start with Haywire EC Units (all of which are explained below).
Similar to I.S., the player may pause the mission by returning to the main menu and resume it anytime, and complete the mission prematurely from the mission menu. Unlike I.S., failing or quitting out of an S3 operation will not end the mission, instead returning the player to the mission menu where the current operation can be restarted. As such, the player can try S3 operations as many times as one wanted until cracked.
Operators[]
Unlike anywhere else, the player can include up to 20 Operators (including the Support Unit) in the Security Mission's squad. However, once the mission is started, the squad cannot be edited for the rest of the mission!
Upon clearing the LT-1, LT-2, LT-4, and LT-5 operations, the player will receive Temporary Reinforcements before starting the next operation, which expands the squad by 2 Operators of the player's choice from a selection of 5 random Operators for each (that can be forfeited). By LT-6, the squad will be made up of 28 Operators.
Which Operators that would appear as Reinforcements are determined by the Operator Strategy selected, chosen when building the initial squad before starting the Security Mission:
- Preferred Plan: Prioritize Operators that are used often by the player, primarily those with the highest promotion.
- Free Plan: Pick every Operator. Using this Operator Strategy also allows for Temporary Recruitment Operators to be available as Reinforcements at times, much like in Integrated Strategies which also extends to the Elite and Reserve Operators.
In an S3 operation, the are three places where an Operator may be.
- Deployment Waiting Zone: Analogous to one's hand on trading card games, the Deployment Waiting Zone is where units that are available for deployment were placed. Up to 12 units can be present in the Waiting Zone; note that summons tied to certain Operators take up space in the Waiting Zone!
- Preparation Area: Analogous to one's deck on trading card games, the Preparation Area is where units that are waiting for deployment were placed. Units in the Preparation Area are moved to the Deployment Waiting Zone by using Transfer Permits (explained below) or certain means, but this cannot be done if the are no available space in the Waiting Zone.
- Recuperation Area: Somewhat similar to one's Graveyard in Yu-Gi-Oh!, the Recuperation Area is where Operators that were knocked out or retreated are placed who can be transferred into the Deployment Waiting Zone through certain means (which is not possible if the are no available space in the Waiting Zone). When the Preparation Area is empty, all Operators in the Recuperation Area will be reshuffled into it.
- When an Operator is transferred from the Recuperation Area to the Deployment Waiting Zone, they can be redeployed immediately; only if KO'd/retreated Operators were transferred right into the Waiting Zone instead of the Recuperation Area through certain means that their redeployment time counts down as normal.
- Regardless of whether Operators in the Recuperation Area are transferred into the Preparation Area or the Deployment Waiting Zone, their DP cost still ramps up as usual.
When an S3 operation starts, the player will have 10 randomly chosen units available in the Deployment Waiting Zone and may shuffle up to 4 units there with random ones in the Preparation Area (during which the game is paused).
Operators can be relieved by deploying one right on top of another (which is so far only possible in S3), in which case the second Operator is immediately retreated and the first is deployed in their place. Because of this, it is possible to deploy an Operator if the Unit Limit is used up, but the Operator must relieve another (e.g. the player cannot relieve a deployed Robot Operator if doing so would exceed the Unit Limit).
Unlike anywhere else, when a deployed Operator's HP is reduced to 0, they will not be immediately KO'd, but rather enters a downed state for 20 seconds during which they are left with 1 HP and are invulnerable, but cannot attack, use skills, block enemies, and be healed in any way, giving the player an opportunity to relieve them. However, do note that certain skills and talents (e.g. Amiya's Chimera, Surtr's Remnant Ash) will not down the Operator, instantly KOing them!
Any changes on the Operators' stats will apply to the next operation in the Security Mission instead of the current one.
Tactical Equipment[]
Tactical Equipments are buffs that can be used to enhance the Operators or supporting their deployment in various ways.
Each class have two Tactical Equipments, A and B, but only one of them can be used at a time, which is chosen during the squad assigment and cannot be changed for the rest of the Security Mission! At first only Tactical Equipment A is available, while Tactical Equipment B is unlocked once the player completes an entire Security Mission for the first time.
When an Operator is relieved, they will pass on all of their Tactical Equipment(s) to the relieving Operator with certain exceptions (see below). However, if the Operator is knocked out or retreated directly (without relieving them), they will lose all Tactical Equipments they had. Passing on Tactical Equipments is important, as the Unit Limit in S3 operations are lower than in elsewhere and the Danger Level (explained below) progressively make enemies stronger, so the Equipments' buffs will help in overcoming the handicap.
A single Operator can benefit from up to five Tactical Equipments at a time, but certain Directional EC Units (see below) allow this limit to be surpassed.
| Class | A | B |
|---|---|---|
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Grants the relieving Operator +20% ATK and +1 SP every 3 seconds | Grants the relieving Operator +40% ATK |
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Grants the relieving Operator +40% DEF and +1 Block | Grants the relieving Operator +25% DEF and +25% Max HP |
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Grants the relieving Operator +40% ATK | Grants the relieving Operator +20% ATK and +20 ASPD |
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All units take 10% less damage | After deployment, revive a downed Operator within range |
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Grants the relieving Operator +40 ASPD | Grants the relieving Operator +25% ATK and +25% Max HP |
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After deployment, return retreated Operators to the Deployment Waiting Zone, and redeployment time -50% | Grants the relieving operator +20 ASPD and +1 SP every 3 seconds |
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After deployment, gain 15 Transfer Permits | After deployment, view 4 random Operators in the Preparation Area, and choose 1 of them to transfer |
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Grants the relieving Operator +20% ATK and +1 SP every 3 seconds | After deployment, converts all Tactical Equipment to Transfer Permits (10 per equipment)[note 1] |
| Additional information | ||
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Operations[]
Each Security Mission is divided into six operations distinguished by the "LT" code, except Security Drill missions which is made up of three operations distinguished with the "TR" code (not to be confused with tutorial operations).
Enemies in S3 operations spawn in three waves, with a 10-seconds Take a Break period or simply break in between them. S3-exclusive bosses who appears in LT-6 operations are excluded from the waves, however.
Transfer Permits can be used to transfer Operators in the Preparation Area to the Waiting Zone at the cost of 10 Permits which increased by 2 whenever Operators in the Recuperation Area are reshuffled into the Preparation Area, up to 20. Players start with 30 Transfer Permits in each S3 operation and can obtain more by:
- Defeating an enemy, which gives 1 Permit.
- At the start of breaks, where the player receives 40 Permits.
- Certain Tactical Equipments:
- Supporter A gives 15 Permits.
- Vanguard B exchanges Tactical Equipment(s) passed by the relieved Operator into Permits at a 1:10 ratio.
- The Reassignment Transmitter allows the player to remove up to two units in the Preparation Area in exchange for 15 Permits for every removed unit.
- Destroying a deployed Contaminated Mineral allows the player to remove a unit in exchange for 15 Permits.
As with Contingency Contract, losing Life Points will not affect the final outcome of an S3 operation, so the player can let one or two enemies leak through if victory is to be assured. However, the S3-exclusive bosses will deduct 3 Life Points upon entering a Protection Objective, thus they must be defeated or the operation will end in an instant failure!
Amplifier Device[]
All S3 operations feature an Amplifier Device, where every 50 seconds of the operation's time (which will be paused during breaks), the Danger Level will go up by 1; each Danger Level usually increases the HP and ATK/DEF of enemies by 25% and 5%, respectively (e.g. at Danger Level 10, enemies have +250% HP and +50% ATK/DEF), but some Security Missions may have different Danger Level effects; hostile devices are not subject to the Danger Level mechanic. As such, the longer it takes to clear the S3 operation, the more difficult enemies will be to deal with.
Each S3 operation has a set Danger Level at the start that increases in subsequent operations and a Danger Level cap that increases as the enemy waves progresses. Fortunately, Danger Level is not carried over between operations.
| Operation | Init. Danger Level | Wave 1 cap | Wave 2 cap | Wave 3 cap |
|---|---|---|---|---|
| LT-1 | 0 | 5 | 10 | 15 |
| LT-2 | 1 | 5 | 10 | 15 |
| LT-3 | 2 | 5 | 10 | 15 |
| LT-4 | 3 | 5 | 10 | 15 |
| LT-5 | 4 | 5 | 10 | 15 |
| LT-6 | 5 | 10 | 15 | 20 |
In LT-3, the Danger Level cap will only be raised once the bonus wave is cleared (i.e. the cap will be of the previous wave instead of the next).
EC Units[]
S3 features unique deployable devices known as EC Units that are divided into three categories: Directional, Special, and Haywire.
All EC Units take up space in the Deployment Waiting Zone and follows the same transferring rules as Operators.
Directional[]
Directional EC Units has both a passive effect that applies throughout the operation and an active effect that applies when the Directional EC Unit is deployed. A Directional EC Unit is chosen before starting a Security Mission and it will be available in all operations of that particular Mission.
Directional EC Units will be transferred into the Recuperation Area after being deployed with some being taken into the Deployment Waiting Zone after being retreated, allowing them to be reused.
After clearing the LT-3 operation, the player can upgrade their Directional EC Unit with one of two Directional EC Components of their choice, modifying its functions or improving its effectiveness.
Some Directional EC Units can only be used in specific Security Missions.
| EC Unit | Use |
|---|---|
 |
|
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Will always be in the Deployment Waiting Zone at the start of the operation.
|
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Can only be used in Under-Construction Dossoles Plate.
|
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Can only be used in Acahuallan Jungle.
|
Special[]
In the LT-3 operation, a Fleet-footed Thief, Shiny Pooloo, or Teary Detective will spawn as a "bonus" wave after breaks which do not deduct Life Points when entering a Protection Objective but awards one of three random Special EC Units of the player's choice; the game will be paused when the player is making the decision, which can be abandoned. Once obtained, the Special EC Unit will be in the in the Deployment Waiting Zone (unless no space is available, in which case it will be in the Preparation Area) and then can be used in all subsequent operations.
Special EC Units will no longer be available for the rest of an operation once deployed, so use them wisely.
| EC Unit | Use |
|---|---|
 |
Transfers a deployed Operator to the Deployment Waiting Zone with reduced DP cost and redeployment time, and retaining their Tactical Equipment(s). |
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Gives 2 Tactical Equipments to a deployed Operator, which will be of their respective class. Does not affect on-deployment Tactical Equipments. |
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Can transfer up to 2 out of 4 random units in the Preparation Area to the Deployment Waiting Zone. |
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Can remove up to 2 out of 4 random units in the Preparation Area in return for Transfer Permits. |
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Can transfer up to 2 out of 4 random units in the Recuperation Area to the Deployment Waiting Zone. |
Haywire[]
Haywire EC Units are detrimental devices only given in the Emergency Resupply mode.
| EC Unit | Use |
|---|---|
 |
Increases the DP cost of units in the Deployment Waiting Zone (including other Concretes but not itself) while in it. Can be deployed for a high DP cost but is invulnerable, does not obstruct enemies, and cannot be retreated – effectively rendering the tile it was on useless. |
 |
Temporarily Stuns friendly units on ranged tiles when transferred into the Deployment Waiting Zone, then transferred into the Recuperation Area. Will never be in the Deployment Waiting Zone at the start of an operation. |
Changelog (Global)[]
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Notes[]
- ↑ The in-game text omits the "After deployment" part, which can be misleading.