Spatial Anomalies
The Cerulean Shockwave was an spatial anomaly that passed through
the Romulan Star Empire in November 2398.  The shockwave was
generated by a quantum explosion of sigma waves on the distant world
of Zirat, and briefly blurred the lines between numerous parallel
universes.  As it traveled, much of the shockwave was dissipated by
gravimetric distortions, however the remnants proved detrimental to
numerous systems aboard Federation starships.  Consequently, the
shockwave proved a major factor in the brief war with the Romulans in
2398.  The vast majority of the Federation fleet was disabled around
Talon IV, allowing the Romulans to seize victory.  The Cerulean
Shockwave was also responsible for disrupting an interspatial flexure
near the Pretorian Cluster; the small flexure contained a small Iconian
scout ship, which later crashed into the surface of Dimovious.  
(“Destinies of Flame and Sorrow” [TFF]).
A gravimetric distortion located deep inside the Alteran Expanse,
formed in 2392 by a massive verteron explosion. The rift served as a
gateway between the Elorg’s subspace realm and normal space.  The
Elorg thusly used the rift as a means to invade Federation space and
reclaim their empire lost to the Iconians 200,000 years ago.  
(“Beginnings” [TFF]).  After several failed attempts (“In the Line of
Fire” [TFF]) the Elorg Rift was collapsed by a Federation/Romulan task
force led by the USS Starlight in January 2397, thusly ending the Elorg
invasion (“Behind Enemy Lines” [TFF]).
Elorg Rift
Cerulean Shockwave
The Tiyzaen Rift is a large rupture in the fabric of space.  It was observed by the USS Majestic
on stardate 98873 (November 2421).  (“Dimensional Analysis” [TFF]).
Tiyzaen Rift
A large interspatial vortex generated by the Drusari to capture and/or
destroy enemy vessels.  The sinkholes were generated from a large
Drusari outpost in the Zukara Segment, and had a range of at least
80,000 light years.  (“The Odyssey, part I” [TFF]).  The Drusari and, to
a lesser extent, the Ghaib, used these sinkholes over the course of
several centuries to remove any vessels that posed a threat to their
gateways.  (“Mystic Invasion” [TFF], “Twilight of the Gods” [TFF]).
subspace sinkhole
A large shockwave that formed in April 2398 after the destruction of a moon orbiting Talon IV.  
The shockwave quickly dissipated without causing damage, but was sufficient to draw the
Federation’s attention to the Talon System.  (“The Fields of Asphodel, part I” [TFF]).
subspace compression wave