Alien Inventory Use

The workings of the Artificial Intelligence (AI) directing the Aliens are shrouded in mystery, particularly its operations on equipment in inventory. Even more so than alien fire and movement, alien inventory operations by the AI are hidden from players. The operations of the AI can't be directly observed, but must be inferred from the outwardly-visible effects (for example at the end of a turn) and augmented by Mind Probe, Psionic Mind Control, or similar techniques. This page is a collection of observations and inferences about the Alien AI.

Normal Things Alien AI Cannot Do

• Pick up anything
• Use any melee weapon (eg Stun with a Stun Rod, attack with a Vibroblade)
• Prime/use Smoke Grenade. (The Proximity Mine may also fall into this category as well as the Flare).
• Use Mind Probe.
• Use Motion Scanner/Medi-Kit.
• Drop anything voluntarily (except when panicking)
• Throw anything other than armed grenades/explosives (various types)

Normal Things That The Alien AI Does Normally

• Attack with alien built-in weapons and alien built-in melee attacks
• Load, reload and fire any ranged weapons normally
  • This includes all human weapons including our so-called 'advanced' technologies. It seems the Aliens have 'Researched' all our weapons and taught their forces not only how to use them, but their strengths and weaknesses!
• Reload its weapon if empty, when spare clip(s) are available, paying TUs to do so.
• Select weapon firing mode Snap, Auto or Aimed. (All have been observed but the rules are TBD)
• If its current weapon is empty and no more clips are available: Switch to another loaded weapon, or to an unloaded weapon that has available ammo, or to a grenade. (Possibly by cheating?)
  • Switching and reloading have been observed for all weapons and all weapon+ammo combinations.
• Prime and throw any standard grenades such as Grenades, Alien Grenades and High Explosives, but not Smoke Grenades or Proximity Mines.
• Use items that are placed in regular inventory slots, including the "magic pocket" (see next section) by first moving the item into the hand.
• Use soldiers' Psi-Amps when controlling MCd soldiers whose psi skill is greater than 0.
• Reaction fire with any loaded ranged weapon currently in its left or right hand.
  • This is a forced, hard-coded reaction for any alien unit that's not currently taking its turn, rather than an action that the AI can choose to take, as it will even work on civilians despite them not having any code that lets them fire their weapons (if they somehow manage to get one) deliberately.
• Pays 15 TUs to reload a weapon, using a spare clip from anywhere in its inventory (but usually from the "magic slot").
• Pays 4 TUs to move objects from the "magic" leg leg slot to either Hand.

Things The Alien AI Does Abnormally

• Ignores Inventory Placement rules, by initially (pre-combat) stacking all its items (apart from weapons in hand) in a "magic pocket" on its right leg (slot 2).
• It is believed that all items are initially stacked in slot 2, but that the AI loads a weapon and moves it into each alien's right hand slot, prior to the start of Battlescape turn 1.

Alien AI Abilities To Be Determined

• Does Encumbrance apply? - May be that Alien TUs break badly if Weight carried exceeds Strength. More investigation needed.
• Are TUs spent in all cases when moving items around?
• When does the AI move items around (regardless whether cheating or paying TUs).
• Unloading a weapon
  • To select a different ammo type
  • To remove a dud round
• Selecting to use, from inventory, a different (eg more powerful) weapon than what is currently held. (Alien AI does this when mind controlling humans. (What are the rules?)
• Drawing, arming and throwing a grenade/explosive, despite holding a loaded weapon. (What are the rules?).
• Changing non-empty ammo clip on a weapon (eg to a more powerful type)
  • If so, what happens to partly spent clips if changed?
• Walk up a ramp? (Zombie has seen Chryssalids walking up the steps in a Lightning, so this is probably true for all transports).
• Ignoring the research status of alien weapons when using mind controlled soldiers carrying said weapons.
• Initiating Psi attack using a mind-controlled human with positive Psi Skill
  • when holding a Psi-Amp
  • when not holding a Psi-Amp
• Flight, especially vertical flight, when a mind-controlled human unit is equipped with a Flying Suit

Things The AI Can't Do, That Can Be Done Under Human or Manual Control

• Placing items anywhere other than the hands or "magic slot"?
• Using Mind Probes, Motion Scanners, Med-Kits, Flares, Smoke Grenades, Proximity Grenades.
• Picking up objects, or deliberately dropping them.

Things The AI Can Do, That Can't Be Done Under Human or Manual Control

• Initiate melee attacks from terrorist units
• Initiate Psi attacks from aliens with Psi Skill but no Psi-Amp

Oddities - Things The AI Can Do, That It Really Shouldn't

• If you use an editor to give a Reaper (large furry terrorist attack animal) any regular ranged weapon (such as a Heavy Cannon or Plasma Rifle) in its Right, er, Paw, the Reaper will attack with that weapon in preference to its built-in melee attack. This may just be reaction fire (like armed Zombies & Chryssalids), not convinced the Reaper is firing during its own turn as well. The Reaper still tries to close to melee range if it can. The prospect of a Reaper packing a Heavy Plasma is not pretty. Nor is a "suicide" Reaper packing a Blaster Launcher to use on you at point blank range.

• • However, the spectacle of a pyromaniac suicide Reaper armed with AC-IN, or equally hilarious, Rocket Launcher-Incendiery, can become QUITE pretty... if your units have Personal Armor or better.

• • This trick does not work with terrorists that already have built-in ranged weapons, as they use their built-in ranged weapon instead.

• Similarly, if you arm Civilians (just with Pistols or Rifles perhaps - most countries do have laws restricting military weapons after all), they will use the weapons in Reaction fire, and will shoot indiscriminately at both X-COM soldiers and Aliens.