Mark / Dash is a summoner spell exclusive to the Howling Abyss. It throws a snowball that, upon impact, deals true damage and over the next 3 seconds the player may reactivate the spell to dash towards the marked target and deals the same damage.
Despite the fact the duration of Mark's debuff refreshes on subsequent applications, summoners still only have their respective 3 seconds to use Dash.
Although not mentioned, the Cleanse summoner spell will not remove the snowflake.
Mark will grant vision of brush (range? PENDIENTE DE PRUEBA) while passing through, and will grant true sight of a hit target. The true sight is granted by the Mark buff, so it is lost when Dash is used.
The cooldown of this summoner spell is automatically reduced to 48 seconds, due to the Howling Abyssbuff, which reduces the cooldown of summoner spells by 40%.
The cooldown can be reduced even more with other sources of summoner spell cooldown reduction.