Trap Runner | Magic: The Gathering
Formats Trap Runner is Legal in
Official Oracle Text for Trap Runner
Official Rulings for Trap Runner
10/4/2004 : This ability will trigger any creature's "whenever this becomes blocked" ability.
9/20/2013 : If a turn has multiple combat phases, the ability can be activated during any of them as long as it's after the beginning of that phase's Declare Blockers Step.