4E: The Platinum Covenant
Tymanther is the home of the Dragonborn in Toril, a rough frontier filled with small towns, military patrols, and a hillscape dotted with the ruins of the former denizens of the area. Tymanther was once Tymanchebar- a small but uniquely independent nation of Dragonborn constantly vigilant against attacks from the tyrannical dragon empire of Skelkor, which they had declared independence from.
When the Spellplague transposed the worlds of Toril and Abeir, a huge region of Tymanchebar was transposed atop the nation of Unther and a region of Mulhorand, completely destroying the nations and their inhabitants. In honor of the Untheric people who were killed, the dragonborn renamed their nation Tymanther.