The Hunyadi Rift was a space-time rupture.
In 2374, the undercover Cardassian transport Solanco was taking a path close to the Rift on it's trip to Terok Nor when (*) caused tensions to rise on the ship between the Cardassian pilot and the Founder aboard the ship. This caused the pilot to veer sharply towards the rift and soon thereafter was killed, causing the ship to head straight into the rift, destroying the Jem'Hadar and (*). (ST - Tales of the Dominion War short story: "Night of the Vulture")