Alien Deployment (Long War)

Battlescape

Similar to vanilla, aliens tend to deploy in tiers, with new aliens being unlocked as time progresses. In addition, aliens will gain substantial bonuses from research, adding health, aim, DR and mobility increases in addition to new perks. Month One will be dominated by Sectoids and Drones, with Thin Men making appearances for Council missions. Month Two adds Floaters, Seekers and random pods of Thin Men to the mix, and is when Terror Missions featuring Chryssalids are first introduced. Be warned, on higher difficulties Floaters and Thin Men show at the end of March.

In May, 2016 EXALT come to the fray, as constant thorn in the side of Xcom, and will likely see the late introduction of Mutons. Following Mutons are Cyberdiscs and Mechtoids, adding a substantial mech element to the mix. Be sure to have HEAT weaponry available by the time these missions spawn, as mech DR is no laughing matter. Berserkers, Muton Elites, and Heavy Floaters follow slowly, with Sectopods and Ethereals making appearances in the late, late game.

Pod counts increase over time, though some rounds can contain as little as two dependent on alien resources. Pods can often be mixed, but typically always include some form of squad leader, a notably healthier member of the squad who may have a higher count of unique abilities. In the later months pods can also include "bosses", who are larger, can boast over twice as many hit points, and have a plethora of skills. Expect Squad-Sight Thinmen, Giant Drones and Chryssalids, and many other towering terrors. Bosses and squad leaders will also occasionaly come with scouting navigators in addition to the regular led pod.

Another particular feature is the existince of a main pod, usually on UFOs and usually the one containing Outsiders. Once triggered all remaining pods will be alarmed and drawn to the location of the main pod. This main be a good way to set up ambushes as well as a sure way to experience a squad wipe if you are not ready for 3+ pods zoning in on your position.

Geoscape

The aliens conduct various UFO missions in the air to achieve their nefarious ends and support their invasion effort. Missions are planned monthly, at the start of the month, and take into consideration Alien Resources and the Threat Level the aliens perceive XCOM to represent. Damaging, shooting down, destroying and/or raiding UFOs is one of XCOMs only means of denying the aliens resources; ironically, doing so also increases threat, so XCOM always finds itself caught between protecting countries from a surge in alien resources and protecting itself from a surge in perceived threat.

The Aliens primary strategy is to invade and take over the globe; they perform this by capturing countries, focusing on those adjacent to their existing holdings first before expanding outward to other continents. Bombing runs and Terror missions are used to spread panic to targeted countries to allow the aliens a window to install a base and start psionically controlling the local leadership, though with enough resources the aliens will attempt Infiltration missions to capture countries directly regardless of panic levels. A captured country withdraws from the XCOM project, denying XCOM its funding & country bonuses. Bases provide other benefits to the aliens, including a steady supply of research and resources. XCOM can return the country to the council by destroying these bases, though locating them requires progressing far enough through the main plot and installing a satellite over the target country. If all council nations leave the XCOM project, XCOM is finished.

The aliens will attempt to Scout out and then Hunt down satellites, focusing first on protecting their own bases from being raided before striking at XCOM-controlled airspace to deny XCOM air superiority. The Aliens' available intelligence on XCOM satellites is abstracted somewhat: they will spend their monthly Hunt missions - representing satellites they've located through other means - to strike at XCOM satellites directly; conversely, they'll spend their monthly Scout missions - representing satellites that have eluded their notice - to try and locate satellites, spawning an additional Hunt mission over and above their monthly supply if successful.

If the aliens consider XCOM a large enough threat, they will begin to focus their efforts on sabotaging XCOM operations directly. Above-average resources and threat is sufficient grounds to get them to send a ground team after your Interceptor Bases, though they'll only start doing so once XCOM has built it's first Firestorm. They'll even initiate an assault on XCOM Headquarters directly, though this requires a few months of maximum threat and resources to get the aliens to take such drastic measures.

The aliens also run various missions across the globe to support their invasion efforts: Research missions to give their air and ground forces a numerical edge in combat and Harvest missions to increase their supply of Resources so that they can field more missions and more powerful UFOs. Denying the aliens the ability to do either helps in the long term, though the need to respond is not as dire as it is for other missions. On top of that, at high enough threat, the aliens will often try to avoid XCOM-controlled countries when harvesting resources, though being forced to choose less optimal sites reduces the return. Lastly, aliens will also conduct Abduction missions - for nebulous and mysterious reasons that may tie in with their overall purpose for invasions. Abduction missions don't particularly help the aliens or hurt XCOM, though failing to respond to them will still spread panic.