Strictly speaking, it's not necessarily required to map and flesh out the entire planet, especially in a fantasy setting that's focused primarily on the events of one particular region. But I find world creation a fun exercise and there's certainly no harm in painting a broader picture.
Ythra is slightly larger than Earth, with a circumference of 30,000 miles. It is also somewhat less dense than Earth, so the gravity is nearly the same, about 1.05 G.Ythra's rotation is the same as Earth's, with a 24-hour day. Its orbital duration is very slightly different: 360 days long, divided into twelve 30-day months, each of which is divided into five 6-day weeks. The similarity to real-world timekeeping is mostly to avoid having to constantly convert back and forth between the fictional time and more familiar real-world time, which would quickly become maddening.
Ythra is a relatively arid planet, its surface being only 40% water compared to Earth's 70%. In general, it's a cool and dry world, with a lot of barren and desert regions, although marshy areas with higher rainfall do exist. Much of Ythra's terrain is rugged and mountainous. Where there isn't desert, xeric regions choked with thick, hardy vegetation are common. Flatter and more fertile regions near rivers and lakes are unsurprisingly given over to farmland. Human and demihuman settlements tend to cluster on coasts and around lakes and rivers, both for better access to the comparatively limited water and for better temperature regulation.
I generated some maps of Ythra. First, a Mercator projection:
Ythra world map, Mercator projection
As this map captures, Ythra's surface is mostly given over to one large supercontinent with two oceans and a few large inland seas, although one could argue that the western land mass which is only connected to the supercontinent by a thin land bridge constitutes a second, much smaller continent.
While Mercator projections allow one to intuitively grasp the contours of land masses at a glance, they have gross scale distortions, greatly exaggerating the size of polar regions. For contrast, here's a spherical view showing each side of the planet:
Ythra world map, General Perspective projection
Finally, what has become my favorite map projection for planetary maps, which was introduced to me by the Traveller RPG, the icosahedral projection. This still allows for relatively easy eyeballing of major features and contours without the gross scale distortions, and I just think it aesthetically looks very cool:
Ythra world map, Icosahedral projection
Lastly, here's the icosahedral map again with the largest geographical features labeled. The supercontinent is called Folthenor and its smaller sibling is called Kel (I've often used the name Kel-Folthenor as the continent where events take place in my fantasy stories), bordered by the Vharis and Marethian Oceans, and the inner seas Lothorin and Dralith.
