It modified the following powers:
- Dual strike (Fighter): While you wield a spear and flail, if both attacks hit, you can immobilize the secondary[U] target until the end of your next turn instead of dealing damage to it.
- Twin Strike (Ranger): While you wield a spear and flail, if you hit one creature with both attacks, you can slide the target one square.
- Dual Strike received errata in July 2009 requiring the secondary target to be different from the primary target. This feat was then updated to reflect the change, and allows immobilizing the secondary target.