From ROI Wiki

Katar is a beverage that is grown and harvested across the entire main continent and is a strong, fiery black drink similar to black coffee, but with a slight smokey, yet earthy flavor. It's moderately high in caffeine and is enjoyed by people from all four of the races. The seeds are picked green, right before they ripen, slow roasted over an open flame, ground, and then steeped to produce its thick, delicious, intoxicating flavor that so many love. However, despite it being popular across the planet, the means by which it is drank depends on region and race. The Yigzan tend to prefer it straight with no additives. The Gorg enjoy it with a bit of green leaf from a local tea like plant mixed in with the katar grounds when it is brewed. The Midazin add a sweet grass native to their area to give it a somewhat lemony twist, while the Sattazin pour rum into theirs to give it an extra degree of kick.