Mind worms in SMAC take the place of Barbarians
from the forerunner Civilization
games. The mind worm proper is a land unit; it is complemented by the marine Isle of the Deep
and aerial Locusts of Chiron
units. These three comprise the "native" unit types of the game world
of Planet. Depending on the Social Engineering
model in effect, the player may have a percent chance to capture (that is, take control of) "wild" (red) native units when attacking. Destroying a wild native unit in combat provides "planetpearls", which increase your treasury (typically 10 "energy unit" currency per lifecycle, per wild unit).
Wild native units spawn from terrain squares containing xenofungus (or at sea, sea fungus). Whereas in Civ, barbarians might capture a city and start churning out offensive units, wild mind worms don't capture bases. Once they have destroyed all defending units, each attacking native will reduce the base size by one, and that attacker will disappear. At later stages of the game, high mineral resource production in a base can result in reversion of a square's terrain improvement in the base radius to xenofungus, sometimes followed by an attack of a huge stack of mind worms. The exact number is based either on the size of the offending base, or the amount of mineral points beyond the ecological safety limit. This takes the place of "pollution" in previous Civ games. (Global warming can still become a problem, but that's beyond the scope of this writeup.)
The following applies to all three "native" unit types. Attack strength and defense strength are based on Psi; rather than the numeric figures displayed for more standard unit types, the Psi units show ? marks. Where other units gain rank (with combat experience, monolith boosts, or base improvement effects), natives are promoted through lifecycle (in combat or at monoliths, but influenced by a different set of base improvements). In Psi combat, the units' lifecycle or rank rating is used in place of attack/defense strengths.
Standard: Mind Worms:
Very Green Hatchling
Green Larval Mass
Veteran Mature Boil
Commando Great Boil
Elite Demon Boil
Xenofungus isn't a unit type, it's a terrain "improvement", and the dominant flora of Planet. Xenofungus squares cost mind worms 1/3 move point, or 2 move points for non-native land units. Wild (red) mind worms spawn from xenofungus, and there's a chance of rousing a wild mind worm any time you try to move a unit into a fungus square. (Even if you move a unit from a xenofungus square and then try to double back to that square, in the same turn, the game engine may spawn a wild native.) Movement through Sea Fungus costs 3 move points, or 1 move point for Isles of the Deep. The same danger of spawning a wild Isle applies when moving through sea fungus squares. The Xenoempathy Dome Secret Project halves the time it takes Former units to clear fungus, lets all land units treat fungus as roads (1/3 move), and reduces movement through sea fungus to one move point. Any unit in xenofungus or sea fungus is invisible to rival units, unless the enemy tries to move into that square. The Sensor Array terrain improvement reveals units in xenofungus squares, in a two-square radius, to the faction within whose borders the sensor is constructed. Finally, until you make certain Tech discoveries, fungus must be cleared before you can build most other terrain enhancements. Resource production in xenofungus squares is similarly limited by Tech progress.
Mind worms may be built once you acquire the Centauri Empathy (E3) Tech advance. They have 1 move point, but they treat xenofungus squares as roads (1/3 move per square). The first mind worm unit you build (rather than capture) triggers the "interlude" screen, where your faction leader tells her "most promising talent" (for the Gaian faction, this talent is named Lindly) to get to the base where the unit was built. If that unit is destroyed by an enemy, this triggers another interlude, where your faction leader goes ballistic and demands that the attacker's home base be disassembled "piece by piece". If you capture this "target" enemy base, it gets renamed in honor of your deceased "promising talent" (again, for the Gaians, "Lindly's Rest").
Isles of the Deep are tremendously flexible: they ignore the move penalty in sea fungus squares, and their Transport capability makes them ideal for harvesting marine Unity pods, as they can thus accomodate Alien Artifact units. Further, they have an effective attack, whereas standard Transport designs have none. Unfortunately, they cannot bombard shore units (a limitation on Psi attacks); from a game balance standpoint, this is perhaps a good thing. They are available for production on discovery of the Centauri Meditation (E5) advance. Hatchlings get 4 move points and a 3-unit cargo capacity. Both move and cargo capacity increase with lifecycle.
Locusts of Chiron are simply the best invasion force in the game. First, they don't crash and burn if they end their move outside a base; second, unlike units based on the needlejet body, they can be used to capture a base once all the defending units are defeated. Finally, they have a decent defense, unlike most standard air units. They are available to build with the discovery of Centauri Genetics (E7).
While "native" units are flexible, they complement, rather than replace, the standard military. They're expensive to build, and they can't be tailored with the special abilities of standard units. Finally, their effectiveness is heavily dependent on your Planet rating (+/- 10% combat values per +/- 1 Planet) and the presence of Psi-related base improvements and Secret Projects. Unless you're playing at the Citizen (easiest) difficulty level, or you play the (green) Gaia's Stepdaughters faction to take advantage of the bonus Planet rating and attendant capture opportunities, an army of native isn't a practical strategy.
Improving your mind (worms): The Biology Lab, Centauri Preserve, and Temple of Planet base improvements will each provide a +1 lifecycle bonus to native units built in that base. The Pholus Mutagen, Voice of Planet, and Xenoempathy Dome Secret Projects each provide a +1 lifecycle bonus to natives built in any of your bases. Native units get combat bonuses in fungus; the Pholus Mutagen extends these bonuses to all your non-native units as well. The Dream Twister Secret Project gives a global +50% to your units' attack vs. Psi, and the Neural Amplifier Project does the same for defense vs. Psi. Finally, your Planet rating in the Social Engineering screen will provide a +/-10% to units' Psi attack/defense for each +/-1 Planet.
While the game will not automatically make non-native units with Psi weapons and armor available, a little tweaking in the Workshop will result in some interesting Psi units. I just like to name them... Psi Stalkers and Dog Boys (from the Rifts RPG) for infantry units, MindSpiders for tank or speeder units, and MindStorms for air units. Again, a "Psi Destroyer" is of use only in ship-to-ship battle, since Psi units can't make shore bombardments. The Hypnotic Trance special ability (available with discovery of Secrets of the Human Brain (D2)) will increase a unit's defense vs. Psi by 50%, and the Empath Song special ability (Centauri Empathy (D3)) does the same for attack vs. Psi. Psi Attack as the main unit weapon is available with the discovery of Centauri Psi (E8), and Psi Defense as the unit armor isn't available until the discovery of Eudaimonia (E12). Remember, the base facilities and Secret Projects that increase native units' lifecycle don't affect your non-native units - they still rely on Command Centers, Bioenhancement Centers, etc. for a starting edge in rank.