The scout was a unit that was unlocked with Free Spirit before the Myriad update came out. The Scout had two skills: Scout and Sneak. Scout allows the unit to explore a 5x5 radius instead of 3x3. Sneak makes the unit not affected by movement barriers like mountains.
Scouts have been removed, due to AI management and tech tree issues. They have somewhat returned in the form of battleships, due to them having the scout skill.