Spine crawler

Spine crawlers are a mobile zerg defensive structure.

Game Unit
Spine crawlers are ground defensive structures that can uproot and relocate. They can only plant themselves on the creep. The spine crawler will stop rooting itself if the creep under it recedes during the rooting animation.

Strategies
Players will want to spread creep onto the map to create more space for their crawlers, such as putting creep onto choke points. The ability to mobilize base defense will also allow for new streamlined strategies that would call for less units, as they can be redistributed across the base depending on the situation. Another use is to use them offensively, moving them forward with the creep as either fall back position or a long ranged attack unit (something which the Zerg otherwise lack), depending on where your enemy attacks.

Like the spore crawler, the spine crawler will slowly die if rooted in ground not covered with creep. They can, however, survive indefinitely without creep as long as they are uprooted.

Development
The concept of mobile defenses in StarCraft II began with the phase cannons, but was transferred to spine and spore crawlers when the phase cannon proved to be unbalanced in testing.

While moving, spine crawlers used to lose their armor and their hit points were reduced to 100.