Nydus canal

The Zerg Nydus Canal serves as a quick transport link from one location to another. The Canal needs two anchoring points, entrance and exit nodes, but once both have been set down, the Zerg forces can travel both ways. Only one Zerg ground unit can be transported at a time, but the process is quick and a large force can travel through in a matter of seconds. The Nydus Canal also has the interesting ability of being able to place its exit node on the Creep of any Zerg colony, friendly or not, which can allow a player to secretly start building a nydus canal in an enemy base. If successful this player can mass his units at will into the opposing player's base. It is likely that the Nydus Canals will no longer exist in StarCraft II, since a mobile unit referred to as a "Nydus Worm" with similar abilities to the Canals made an appearance in an early video.