Currently skirting the edge of the maelstron, near the end of Agalon's Arm, is an anomaly dubbed Tasiv's Tear. Unlike normal rifts, this anomaly has remained permanently open for the now near 450 years that's passed since its creation and shows no signs of ebbing out anytime soon.
Attempts to manually close it have been unsuccessful, but the modified riftgating technology employed at the end of the Tasivian Scourge has managed to prevent darkverse lifeforms from exiting the rift for as long as it's been regularly maintained. For this reason the anomaly keeps on being monitored and is presently considered relatively harmless. In recent years there been clear signs of the rift growing while being in close proximity to the maelstrom which, while concerning, so far has been manageable by adjusting the riftgating technology to compensate for its increasing size.
History
The rift was originally artificially created close to the world Agalon some 450 years ago, and led to a disastrous event often referred to as the "Tasivian Scourge" in common mouth.
According to historical records, an experimental reality cutter was stolen and used by the infamous pirate Tasiv as she tried to escape from pursuers. The device imploded on use and opened a rift of massive scale that afterward couldn't be closed again. While it was never made clear whether Tasiv and her crew survived, one can assume her riftcraft, its crew, and the experiemental reality cutter were all annihilated in the implosion. Though there's plenty of spacer tales to find that regale a different fate for Tasiv and her crew.
The Tasivian Scourge
Directly following the rift's opening hostile darkverse fauna unexpectedly began to flood out of it and attack anything they came across. Agalon and nearby locuses were forced to be evacuated, and thousands of lives were lost either escaping or fighting the aggressive alien lifeforms.
The flooding continued for nearly six years until it was made possible to employ modified riftgating technology to encase the anomaly and prevent further influx of its native fauna. Another eight years were needed to clear out lingering hostiles. During aftermath evaluations it was judged that, since Agalon had been so severely ravaged, and it's system didn't hold much of value otherwise, it wasn't considered worth the investment to engineer it back to being habitable. Most surrounding locuses were also only briefly scavenged and then abandoned.
Normally a stable rift or wormhole would seem like an economic and scientific boon, but I can see why they've been trying to close this rift! I like that this stable rift was created by a pirate fleeing! I love unintended consequences. Hopefully the modified riftgating technology holds up.
So far, so good. ^^ And yeah, they sure are! Stable artificial rifts are needed for reliable interstellar travel, but large ones requires a lot of security measures to avoid disasters. And unlike this anomaly, they can usually be emergency closed by cutting the power source feeding them. :)