Remove as many Runes as you want without paying a single Mana Stone on Mar. 1st.
Event Details
Global server: From Mar. 1st 12am – Mar. 2nd 12am (PST)
Asia server: From Mar. 1st 12am – Mar. 2nd 12am (Taiwan Standard Time)
* Please make sure to restart the game to take advantage of this event if you’re logged in at the start of the event.
Source: http://www.withhive.com/