|“||Alien terror attack in progress. Strong civilian presence, take care to avoid civilian casualties. Failure will have severe political consequences for XCOM.||”|
- Approach civilians to enable evacuation
- Minimize civilian casualties
- Neutralize all hostile targets
This mission type first appears during the second month and becomes active as part of the "random event pool" for each month of the game after that. When a terror event is detected, XCOM has 30 hours to start the mission before it is considered ignored and is no longer available.
Terror Site missions take place in densely populated urban areas. The layout is randomly chosen from a predetermined pool of 9 maps (11 in XCOM: Enemy Within), which are all available regardless of the nation the mission occurs in. Some of the maps are also shared with Alien Abduction missions.
Urban areas typically consist of tight spaces with a lot of cover and multiple obstructions. This makes them good for mobility and flanking. Some maps also have multi-level buildings. Having soldiers equipped with grappling hooks via Skeleton Suit or Ghost Armor can be very helpful.
Depending on the stage of the alien invasion, this mission type can feature many alien species, including: Berserkers, Chryssalids, Cyberdiscs, Drones (as escorts), Floaters, Heavy Floaters, Mutons (as escorts), Muton Elites, and Sectopods. Due to civilian presence, these are also the only missions in which the player may encounter Zombies in abundance.
A terror mission's difficulty rating is always "Very Difficult," and the number of aliens is determined by the game difficulty. The first Terror Site mission consists of 25-50% fewer enemies than usual, depending on the game difficulty. Each enemy pod may consist of one to three aliens.
- Main article: Squad Tactics (XCOM: Enemy Unknown)
At the start of the mission, there are 18 civilians spread across the map, whose survival influences the mission rating and panic reduction reward. Civilians can be rescued by moving a soldier close to them. The civilian flees towards the Skyranger, potentially revealing alien pods along the way. They do not, however, trigger alien reaction fire while fleeing. There is no need to individually rescue all of the civilians, as any that are still alive when the aliens have been eliminated and the mission ends are automatically counted as rescued. Explosives should be used with care, as they kill any civilian caught in the blast.
Alien units actively roam the area, killing any civilian they find. When encountered, most species prioritize a quick and easy civilian kill over tougher XCOM soldiers, even if the soldier is closer. Berserkers, Cyberdiscs and Sectopods only aim for XCOM operatives and ignore civilians; in Enemy Within, Chryssalids often go for the closest target, be it civilian or XCOM. Because the mission is considered a success as long as at least one civilian is saved, it may be advisable to prioritize squad survival over civilian survival.
In Enemy Within, after the Sectoid Commander Autopsy is completed, Mimic Beacons can attract alien pods not in combat away from civilian targets or into traps. Chryssalids are especially prone to falling for the lure.
Chryssalids and ZombiesEdit
Many Terror Site missions feature Chryssalids, which comes with an additional challenge. Civilians and soldiers killed by a Chryssalid's melee attack may turn into extremely tough Zombies after one turn. To avoid being overrun, it is preferable to make Chryssalids priority targets when encountered on these missions.
The chance that a Chryssalid's kill will result in an implantation during a Terror Site mission is determined by two factors: Whether or not the kill occurred in view of an XCOM soldier, and by the game's difficulty setting. For all difficulties, an observed kill will result in a Zombie. The chance that an unobserved kill results in an implantation depends on the difficulty setting:
Confident players in a strong position may consider letting Chryssalids kill civilians for a few turns - more Chryssalids means more Chitin Plating and more experience. So long as one civilian is saved the mission will not be considered a failure. Obviously this is only viable when panic reduction in the terrorized continent is not a concern. Note that an implanted victim will not prevent the mission from ending, as long as it has not yet risen up as a Zombie.
The number of citizens rescued determines the mission rating: 
|Citizens Rescued||1||2 - 8||9 - 13||14 - 18|
|Citizens Rescued||1 - 8||9 - 13||14 - 18|
|Panic Reduction *||2 / 0||3 / 1||5 / 2|
* Nation panic reduction / Continent-wide panic reduction
Aborting, failing (rescuing 0 citizens or all soldiers KIA), or ignoring a Terror Site mission results in the target nation leaving the Council; these missions should not be failed or ignored if at all possible.
- If playing with game mods that increase alien pod size, additional enemy units that would focus on XCOM exclusively may target civilians instead. This happens often with Cyberdiscs.
|XCOM: Enemy Unknown Missions|
|Alien||Abduction • Terror Site • UFO Crash Site • UFO Landing Site|
|Council||Asset Recovery • Bomb Disposal • Site Recon • Target Escort • Target Extraction|
|DLC||Slingshot: Friends In Low Places • Confounding Light • Gangplank • Progeny: Portent • Deluge • Furies|
|Storyline||Alien Base Assault • XCOM Base Defense • Overseer Crash Site • Temple Ship Assault|
|Other||Starter Mission • Tutorial • Meld Tutorial • Covert Operations • EXALT Base Raid|