Nydus worm

The nydus worm is a zerg transport strain.

Overview
A nydus worm (or similar variant) was observed on Urona Sigma in 2502. This organism was capable of tunneling through rock to reach its targets, creating a passage for smaller strains to follow. They didn't require creep on the surface of its point of emergence.

By the Second Great War, the nydus worm was an evolution of the nydus canal. These worms live inside a nest-like structure called the nydus network and can travel from the network to any nearby location that is covered by creep before emerging, in the process creating a tunnel beneath the battlefield. This huge creature is capable of stretching itself out to prodigious lengths to support the tunnel with its own skin and ribs. Zerg warriors can enter the tunnel via either the worm’s head or network, and can travel through the worm at great speed due to a combination of peristaltic motion and chemical stimulants that direct their movements. When combined with the creep-spreading tactics of queens and overlords, nydus worms pose a grave threat to areas previously thought to be secure.

Game Structure
The nydus worm can spawn on any 3x3 patch that is clear of the fog of war. Deploying on creep is optional.

The nydus worm grants access to the "nydus system" through the UI. Nydus worms and networks act as portals into and out of the system. Units are loaded into the system, and may not be attacked while inside. Loaded units are lost only when all portals are destroyed.

Air units, mobile crawlers, and allied units cannot be loaded into the system.

The nydus worm can be used to transport as many units as are selectable. These units are visible within the system. However, the UI displays only the first couple of units per supply-level.

Unloading all units from a nydus worm makes them exit one-by-one in the order they entered the system. All units, regardless of properties, take the same time to unload. The unload command does not affect units who enter the network while unloading is in progress.

Each worm can be given a rally point. Units which exit that particular worm automatically attack-move to that point.

When a nydus worm finishes spawning, a screeching sound and a text warning are issued to all players. This alerts players. This is unlike the nuke warning, which gives time to react.

A nydus network may spawn only one nydus worm at a time, although spawning may be queued. Having multiple nydus networks allows multiple nydus worms to be spawned simultaneously.

Strategies
Nydus worms can quickly transport units between multiple zerg bases, in a manner similar to nydus canals. A pool of units can be kept in the "nydus system" to emerge at a moment's notice at any of the system's entrances. This can be used to move drones to and from expansions.

Use multiple nydus worms to attack an enemy base; single worms are easily destroyed due to their low hit points. Spawning multiple worms near multiple bases may be used to feign attacks and test defenses; troops can be sent against bases which are not reinforced.

Units unload in the same order they are loaded; manipulate the load order so an attack is spearheaded by the most appropriate units.

Blizzard has noticed that nydus worms aren't being as used as often as they would like. They are considering making changes to the unit, but would like to keep it distinct from the overlord, in regards to being a riskier, but more effective zerg transport in-game.

Heart of the Swarm
Blizzard is planning on allowing players to produce different kinds of nydus worms. Examples include a worm that can spew creep across several screens to create a zerg assault highway as well and a worm that attacks only enemy buildings which are used as a ground based zerg base raider.

As of September 2012 these new versions have yet to appear, and were eventually canceled, though variant strain data does exist in the game's beta files.

Variant Strains

 * Creep tower
 * Meinhoff worm
 * Nydus destroyer