Beacon of Doom is a 19th level cleric Daily prayer that was introduced in Divine Power.
Beacon of Doom
Cleric Attack 19
With a resounding strike, you denounce your enemy. It crumples under a flurry of attacks from your friends.
Melee weapon
Target: One creature
Attack: Strength vs. AC
Hit: 2[W] + Strength modifier damage.
Miss: Half damage.
Effect: The target takes a -4 penalty to all defenses (save ends).
Aftereffect: Each ally within 5 squares of the target can make a basic attack against it as a free action.
Each Failed Saving Throw: One ally within 10 squares of the target can make a basic attack against it as a free action.