An unopened fluidic gate.

A fluidic gate was a type of organic structure in space used by Species 8472. These "gates" were capable of forcing an entry into fluidic space and allow reinforcements in the form of heavy warships to pass through. These gates were fixed structures and were incapable of movement. (ST video game: Armada II)

Previously, Species 8472 were known to use a quantum singularity as an entry point into their realm, so it may be that these fluidic gates were present on some such singularities.
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