UFO Incursions (Apocalypse)
Alien Craft Type and Quantity Appearing in Mega-Primus
In General
Aliens send their craft through a 'portal', called a Dimension Gate, appearing at random locations and random positions within the cityscape as time progresses. It is an invunerable device.
Alien Craft Growth Limits
UFOs are 'grown' in the Alien Dimension at the start of the week of only a certain quantity and type dependant on the number of weeks elasped in the game:
Maximum UFO Quantity
| Week |  |
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|---|---|---|---|---|---|---|---|---|---|---|
| 1 | 9 | 9 | ||||||||
| 2 | 2 | 4 | 3 | 2 | ||||||
| 3 | 2 | 4 | 2 | 2 | 3 | |||||
| 4 | 1 | 2 | 1 | 1 | 2 | 2 | ||||
| 5 | 1 | 1 | 1 | 1 | 2 | |||||
| 6 | 1 | 1 | 1 | 1 | 1 | |||||
| 7 | 1 | 1 | 1 | 1 | 1 | |||||
| 8 | 1 | 1 | 1 | 1 | 1 | |||||
| 9 | 1 | 1 | ||||||||
| 10 | 1 | 1 | ||||||||
| 11 | 1 | 1 | 1 | 1 | ||||||
| 12 | 1 | 1 | ||||||||
| 13 | 1 | 1 | 1 | |||||||
| 14 | 1 | 1 | ||||||||
| 15 | 1 | |||||||||
| 16+ | 1 | 1 | 1 | 1 | ||||||
| Maximum | 15 | 15 | 6 | 6 | 6 | 6 | 6 | 6 | 4 | 2 |
Alien Mission: Schedule
At the start of each week (Monday), the Aliens randomly choose days and times within this new week to perform a variety mission types: Infiltration, Search, Bombing, Overspawn Drop. When a mission is due according to Monday's timetable, the aliens will choose a mission style dependant on importance (the percentage chance) and the number of weeks elasped in the game:
Mission Schedules
| Week | Infiltration | Search | Bombing | Overspawn Drop |
|---|---|---|---|---|
| 1-3 | 100% | 0% | 0% | 0% |
| 4 | 90% | 0% | 10% | 0% |
| 5-6 | 80% | 10% | 10% | 0% |
| 7 | 70% | 10% | 10% | 10%* |
| 8 | 50% | 20% | 10% | 20% |
| 9-11 | 40% | 20% | 20% | 20% |
| 12 | 30% | 30% | 20% | 20% |
| 13 | 30% | 20% | 30% | 20% |
| 14 | 40% | 20% | 20% | 20% |
| 15-18 | 30% | 20% | 20% | 30% |
| 19 | 20% | 20% | 30% | 30% |
| 20+ | 10% | 40% | 20% | 30% |
Once a mission is selected, the aliens will allocate the UFOs required (if available) in the Alien Dimension to immediately spawn into Mega-Primus.
Note: An Overspawn Drop for Week 7 is an error in the game since the craft needed, a Mothership, is not yet available.
Alien Missions
Any alien mission chosen in the schedule will only commence if the required UFOs are present in the Alien Dimension, that is, the mission will only start if the needed craft are available, and if not, the mission will not start and the 'time and day' mission slot is forfeited.
The alien craft will materialise from the dimension gates in sequence (all Primary craft, all Escort craft, all others) according to their selected mission. When the first craft has spawned in, the next craft due will choose a gate randomly of the three, until all are present. (A save/load between each spawn will again randomise the gate choice for the UFO due to appear next.)
The alien crafts listed in "Escort" are assigned protection duty of the "Primary" group's leader, hence, the first craft that spawned into the city is (always) the leader of all primary craft. If the leader is lost when under escort, the assigned escorts will select the 'second in command' primary craft as the new leader... until all primaries are either shot down or have escaped back into the gates. If no more (viable) primary craft are present, any escorts remaining will return to the gates and leave. Escorts do not escort other designated escorts. Primary UFOs will proceed with their mission regardless if an escort is available.
Important: The column "Mission" in the following tables is not based on elapsed weeks but the variety of craft types that will partake in each section's mission type. The selection of a group will start at the bottom and move upwards through the list until the UFOs present in the Alien Dimension can fulfil the particular mission's grouping requirement. If a group cannot be formed, the mission will not proceed.
Infiltration
Alien crafts used to insert alien lifeforms into buildings:
| Mission | Primary | Escort | Bombing | Week |
|---|---|---|---|---|
| 1 |  |  | 1 | |
| 2 | | | 1 | |
| 3 |  | 2 | ||
| 4 | |  | 2 | |
| 5 | | | 2 | |
| 6 |  | | 4 | |
| 7 |  | | 3 | |
| 8* | | 4 | ||
| 9 | | | 3 | |
| 10 | | | 3 | |
| 11 | | 4 | ||
| 12 | | | 4 | |
| 13 | |  | 5 | |
| 14 | |  | 8 | |
| 15 | | | | 8 |
| 16* |  | | 7 | |
| 17** | | | | 7 |
| 18 | | | 7 | |
| 19 |  | 8 | ||
| 20 | | | 8 |
*These fleets will never appear, as the ships required will also fulfil a higher-priority fleet.
**This fleet can appear as long as the aliens have at least one Battleship and one Escort Ship (though two Battleships will still appear in Mega-Primus). This is the result of an error in the allocation of available crafts - instead of checking whether there are two Battleships, it checks whether there is one Battleship twice.
Search
Alien crafts used to search a building for an X-Com base:
| Mission | Primary | Escort | Week |
|---|---|---|---|
| 1 | | 5 | |
| 2 | | 5 | |
| 3 | | 5 | |
| 4 | | 5 | |
| 5 | | 5 | |
| 6 | | 5 | |
| 7 | | 5 | |
| 8 | | 5 | |
| 9 | | | 7 |
| 10 | | | 8 |
- Base Assault fleets can appear from Week 5 onwards.
Important: Once an X-Com base has been located, the "Search" mission style becomes an 'X-Com Base Attack' mission style with the primary leader craft (usually) only being used (and maybe some escorting craft) since the aliens don't need to search so many buildings now, they don't need to use so many craft!
Bombing Buildings
Alien craft groups assigned for building destruction of hostile organisations in Mega-Primus.
| Mission | Primary | Escort | Week |
|---|---|---|---|
| 1 | | 4 | |
| 2 | | | 4 |
| 3 | | 5 | |
| 4 | | | 4 |
| 5 | | | 5 |
| 6 | | 6 | |
| 7 | | | 7 |
| 8 | | 9 | |
| 9 | | 9 | |
| 10 | | 8 |
- Bombing fleets appear from Week 4 onwards.
Overspawn Drops
Exactly what it sounds: An Alien Mothership (usually with escort craft) is sent to drop an Overspawn to attack the city directly. This type of mission can *only* occur if the aliens currently have a mothership available to deploy.
| Mission | Primary | Escort | Bombing | Week |
|---|---|---|---|---|
| 1 | | 8 | ||
| 2 | | | 8 | |
| 3 | | | | 8 |
| 4 | | | 8 | |
| 5 | | | 11 |
- Overspawn drops can appear from Week 8 onwards.
- A fleet with two Motherships is guaranteed to be on an Overspawn Drop mission.
WIP placeholder
The Roles
Primary ships will give up on their mission if they receive too much damage, and will attempt to retreat.
Some UFOs on the Infiltration and Overspawn Drop tables are listed as "Bombing" craft. These craft will bomb a building, as though on an Bombing mission.
Destroying the Control Chamber building permanently halts the production of alien craft. It also triggers a special incursion not found on these tables - the next time an alien mission is scheduled, all remaining UFOs (except Probes) will swarm out of the Dimension Gates and start tearing down Mega-Primus as though on a very large Bombing mission. This final battle is typically referred to as "the Apocalypse mission".
dard type of UFO incursion for the majority of the early game, which peters out as the weeks go on in favor of more direct aggression. Infiltration fleets consist of one to three primary craft, usually with escorts to protect them (as seen on the table below). When they appear in Mega-Primus, the primary craft will fly directly to a pre-selected target destination, hover over it for several seconds and attempt to deploy a squad of aliens to infiltrate the building via a transport beam (i.e. 'the grey tube'). Destroying the craft before it reaches its destination will prevent this. If the tube has already appeared, it is possible to prevent the UFO from succeessfully completing its transport by destroying it before the beam has finished. UFOs which successfully deposit their troops will then immediately move to the dimension gates to return to the Alien Dimension, leaving players to have to send squads to investigate those buildings for aliens. If left unchecked, the target organization's infiltration percentage will go up after several hours and the aliens may continue to spread to nearby buildings and organizations, creating an even bigger problem for X-Com over time. When a primary UFO craft for this mission type escapes via the dimension gates, that craft's assigned escort(s) will then immediately attempt to escape as well (this rule holds true for most if not all incursions).
If the Aliens choose to target an X-com base for infiltration, this will trigger a base defence mission instead.