The Infested Terran is a rarely-used Zerg suicide unit produced from the Infested Command Center, which is created by Queens from damaged Command Centers. Similar to the Scourge, it is a unit that sacrifices itself exploding on targets, doing a large amount of damage, but with the damage dealt to a ground, rather than air, unit. The splash damage is akin to that of a Siege Tank and is sufficient to destroy any other land unit.
The Infested Terran has similar health and speed to the basic Terran Marine, but has costs significantly more in minerals (+50) and gas (+50). Also unlike the Marine, the Infested Terran does not have range attack capabilities. Its fragility and cost make it a difficult unit to use effectively, even if an Infested Command Center is somehow obtained. Due to its weak health and speed, it is often challenging for the Zerg player to direct the Infested Terran near enough to target an enemy army, except during a confrontation in which the opponent does not fire upon it.
Infested Terrans do not deal damage if killed. Their effectiveness must be as a result of a targeted command by the Zerg player. If attack-moved on screen, rather than the Minimap, the Infested Terran will blow up when it reaches its destination, regardless of whether an enemy unit or building is present.
The Infested Terran does not have any upgrades to be researched.
The use of Infested Terrans is heavily limited by the difficulty of procuring Infested Command Centers and their high cost. As a result, it is rarely seen in competitive play, and rarely been seen in professional competition. The Infested Terran is a sure kill upon detonation. It can be partnered with Overlords to better ensure survivability, if the Zerg manages to produce them, as the Overlord can avoid opponent fire by flying around obstructions. Additionally, the Overlord can sustain much higher hit points than the Infested Terran. Infested Terrans not only destroy out all units due to the 500 damage dealt, but also most buildings if they reach their target.
Infested Terrans also deal splash damage to the Zerg player's own units, like the Siege Tank, so sending multiple units at once can be disadvantageous as the damage dealt by the preceding Infested Terran may also destroy nearby/surrounding Infested Terrans with the splashed friendly fire. As such, it is difficult to escort Infested Terrans with other Zerg ground units, as the splash will kill large concentrated numbers of the Zerg player's Zerglings and can easily kill Ultralisks as well. Thus, Infested Terrans may pose a great threat to the Zerg player's own army, and must be handled with care. As a result, in 1v1 matches, Infested Terran are typically relegated to directed to travel by itself without escort from the often distant Infested Command Center to the opponent's forces.
Unfortunately, the best ways to keep an Infested Terran alive long enough to kill itself lie with other races, in the form of the Defensive Matrix, Hallucinations, or the cloak of an Arbiter which are only possible in allied games. Therefore, Infested Terrans are most effective at ambushing and capturing the enemy off guard through the use of Burrow, Dark Swarm, and/or the distractions of allied units well out of harm's way.
The Infested Terran cannot appear normally in the solo ZvZ match-up without Command Centers for Queens to infest, but with map Holy World and related maps that feature unclaimed/neutral Command Centers, there is a possibility of seeing one, although their utility is still very low. Infested Terrans are easily killed and intercepted by Mutalisks, which are the most popular forces in the ZvZ match-up. The chance of a Zerg player taking the costs of morphing in a Queen's Nest and getting a Queen instead of any other unit is almost none.
Although in theory, Infested Terrans can be used to drop into a cluster of SCVs at a Terran expansions, kill off a large number of Marines & Medics, and destroy Supply Depots in one sacrificial hit, Infested Terrans do not see much usage because most Zerg players would rather have an extra Lurker or Drone instead of morphing a Queen. M&M have a very high damage per second, thus they can quickly kill any approaching Infested Terran without being exposed to its explosive damage. As such, its vulnerability coupled with the poor AI that comes with the clumsy movement/pathing of the Infested Terran make the unit to be rarely built. Primarily, these are used as humiliation tactics in TvZ.
Although it is normally impossible for Infested Terrans to make an appearance in the PvZ match-up, Holy World makes this possible by introducing a neutral Command Center. Infested Terrans are far more effective in PvZ, due to the Protoss's lack of units that can take down Infested Terrans before they reach their target. That is, many Photon Cannon or Dragoon shots would be necessary, unlike a Siege Tank or M&M strike. The Infested Terran can be used in conjunction with Overlords, protecting the Infested Terran and dropping them inside Protoss bases and Probe lines. They can destroy a Photon Cannon with a single explosive hit, as well as any ground unit in a single explosion, and are most effective when detonated when targeted at a large cluster of units.