The scout was a unit that was unlocked with Free Spirit before the Myriad update came out. Scouts had two main abilities: Scout and Sneak. Scout allows the Scout to explore a 5x5 radius instead of 3x3. Sneak makes the scout 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.