Travel is as arduous as it is dangerous. Many perils await on the trail, from the elements to roving bandits. It is common for the peoples of Isyra to avoid far-flung treks for this reason. For those willing to risk the dangers, often their journeys are made easier with riding animals, caravans, or even sailing ships. The main benefit of riding and sailing is the speed, quickening the overall pace of travel several times over. Further, such actions can even open up routes that a traveller on foot would not normally be able to consider.
At their most basic, vehicles and mounts will have multipliers that apply to travel speed, along with favored terrain that they can cross. For example, a horse might offer a x3 to travel speed, and would favor steppes and grasslands. In less favorable terrain, the horse would be slowed to x2, or even standard travel speed.
For the most part, a character will not need to make a riding or sailing check to ensure that they do the job correctly. If traveling in unfamiliar or uncharted territory, at least one character in any given group would need to make a (Mind + Nature) navigation check against a difficulty determined by the storyteller. The difficulty can rise and fall based on weather conditions, tools available, etc. A good baseline for the difficulty would be 5 to start.
Navigation is something that even travellers on foot have to consider, but it is especially important to sailors. Getting lost on the featureless waves is a real fear, and a common element in Isyran adventure stories. Many who lose their way at sea never make it back home again.
In combat, mounted characters use their steed's movement rather than their own. Further, that mount's speed multiplier affects its overall speed as well. For example, if a horse has a Body of 5, and has a multiplier of x3, it can move at 15 meters per round. Dashing, the horse could move a total of 30 meters per round.
While controlling a mount in combat, a character needs to roll a (Body/Spirit + Nature) check to keep the mount under control and in the fight. As long as the mount is under control, this does not take up an action for the character. However, gaining control of a mount will take a successful check, and both of a character's actions for a round.
Ships and Vehicles:
Crewed vehicles such as ships often take multiple people to function. Commanding such vessels requires either cooperative rolls or the formation of battle groups in order to pilot them successfully. This is especially true for combat, in which characters will have to fulfill particular roles to utilize the vehicle to its fullest. Smaller boats and vehicles might be able to piloted by a single individual. In these cases characters need not worry about taking collaborative actions, and instead can roll their own dice pools as needed.
Like mounts, vehicles also use their own speed modifiers to determine their movement in combat when applicable. Most vehicles will use the Body attribute of the animal drawing it, but others may have other methods of motion besides animal power. Such vehicles will have a baseline speed included with their modifier with which players can calculate their maximum distance in a round.
(Spirit/Mind + Command + [cooperative dice]) is the general roll used for any action using a crewed vehicle in combat. Cooperators contribute their Nature, Craftsmanship, Projectiles, or Melee skills most commonly, depending on what role they are filling for the crew. A craftsman might set about fixing things, whereas a warrior might be fighting off a boarding party. For particularly large vehicles that are crewed by battle groups, the roll is (Spirit/Mind + Command + Crew's Drill).
Individually piloted vehicles simply need a (Spirit/Mind + Nature/Command) roll to function. Of course, additional actions might be needed to attack or defend from the vehicle as needed, depending on its design.