Speed Potion

 is an uncommon potion which brings up a benefit effect upon use. The effect increases non-combat movement speed by 30 points for 1 minute and 30 seconds.

There exists separate Speed of Youth Potion which has identical effect, but cannot be stored in bank or traded.

Consuming 100 will award achievement Speed Demon and title Speedy.

This potion is now more or less phased out. You can now ride mounts in most dungeons, like in Golden Labyrinth that has huge long corridors. Also login buff since TERA: Fate of Arun gives extra running speed while not in combat.

Source
This potion is obtained via:
 * 3 is given upon character creation
 * reward from the quest
 * sometimes obtained when gathering from energy crystals

As of gathering changes in December 2018 this potion no longer drops when gathering. There are no known sources or quests that give these, also this potion cannot be crafted.