Dragon Tail inflicts damage and has decreased priority. In a Trainer battle, it will switch out the target to the next Pokémon in line that has not fainted (if there is one). In a wild Pokémon battle with a single wild Pokémon, this move will cause the battle to end if the user's level is equal or greater than the target's.
If using this move causes the user to faint (such as if the target is holding a Rocky Helmet or has the AbilityRough Skin or Iron Barbs), the target will not be forced to switch.
Dragon Tail will fail to end wild Pokémon battles or switch out the opposing Trainer's Pokémon if the target has the Ability Suction Cups, is under the effects of Ingrain, or has Substitute set up.
The target is knocked away, and a different Pokémon is dragged out. In the wild, this ends a battle against a single Pokémon.