The Reach

From Asoiaf

The Reach encompasses the soutwestern part of Westeros.

Qhored, King of the Islse ruled the Arbor and Oldtown, but his descendents lost them.

Mern, last King of the Reach, perished at the Field of Fire. His steward, Harlen Tyrell, surrendered Highgarden to Aegon. Aegon granted Harlen Highgarden and dominion of the Reach.