You grab the enemy's attention with an aggressive strike to give your allies a chance to set up their own attacks.
Encounter ✦ martial, weapon
Melee weapon
Target: One creature
Attack: Str vs AC
Hit: 1[W] + Strength modifier damage
Effect: One ally you can see can shift half his or her speed as a free action to a square where it has cover or concealment and make a Stealth check to become hidden. Before the end of your next turn, that ally gains a +3 power bonus to his or her next damage roll made against an enemy from which he or she is hidden.
Set the Trap is an encounter power available to warlords at 3rd level.
Set the Trap was introduced in "Class Acts: Warlords" by Robert J. Schwalb in Dragon #384.
CharOp Evaluation: Bad [Char-op Warlord]
The attack itself isn't very strong and has way too many conditions for a measly +3 damage payoff. There might be some incredibly niche builds if you have an ally with good stealth who desperately wants to be hidden, but in general, This is a bad option.