Shortly after the Galactic Empire began transitioning to TIE Starfighters as their primary fighters Darth Trepid, buried deep in the unknown regions, got the plans for them. After a couple years he upgraded the fighters using the advanced Rakataan, Kwa, and Gree technology he had discovered and other technology that his scientists developed.
One of the classes he developed was the TIE Dread. This assault fighter packed quite the punch.
It had medium shields, hyperdrive, and cloak. In addition to the TIE Trepid's four wingtip canons and four ion canons, two small canons, and missile launchers, the TIE Dread boasted two large canons in it's pylons, four additional missile launchers, two tracking lasers for extra guidance, and two automated turrets. Don't forget it had the Rakatan/ancient Sith technology of self-healing metal.
In real life this is inspired by my favorite real life fighter, the P-38 Lightning.
Here we see some TIE Trepids in formation with the TIE Dread.