Bone-Breaking Whip (4e Feat)
From D&D Wiki
Bone-Breaking Whip [Racial]
One swift crack of your tail can shatter bones and dislocate joints.
Prerequisite: Iejirisk, Str 15 or Dex 15, tail whip racial power
Benefit: Permanently increase the damage die of your tail whip racial power by one (from 1d6 to 1d8, for example). In addition, on a successful hit, the target is slowed until the end of your next turn.