Improved Misty Step is a heroic tier feat available to warlocks with a fey pact and an Intelligence score of 13 or higher.
Normally, a warlock with a fey pact can teleport 3 squares as a free action when an enemy under the warlock's Warlock's Curse is reduced to 0 hit points or fewer. A warlock with the Improved Misty Step feat may teleport an additional 2 squares in this circumstance.[PH:198]