Clamp.....

Type Water
Category Physical
PP 10 (max. 16)
Power 35
Accuracy 75%

Clamp inflicts damage for 2-5 turns. There is a 37.5% chance that it will attack for 2 turns, a 37.5% chance that it will attack for 3 turns, a 12.5% chance that it will attack for 4 turns, and a 12.5% chance that it will attack for 5 turns. Though technically only the first attack can critical hit, every attack during the duration will do the same amount of damage. While Clamp is in effect, the target will be unable to attack, and if the user of Clamp attacks before the target when used, the target will be unable to attack during that round as well.
Damage inflicted by Clamp's continuing duration is done after recurrent damage. If the user switches out before Clamp's duration ends, the target will be unable to attack during that turn. If the target switches out before Clamp's duration ends, Clamp will automatically be used against the incoming Pokémon, deducting an additional PP from the move. If at such a time Clamp has 0 PP, Clamp will still be used against the incoming Pokémon, but the current PP of Clamp will roll over to 63, and full PP ups will be applied to it.
Even if Clamp misses, it will negate the recharge turn normally required for Hyper Beam. Additionally, if the user of Clamp attacks before the user of Hyper Beam during a recharge turn and the use of Clamp misses, the user of Hyper Beam will automatically use Hyper Beam during that turn. If at such a time Hyper Beam has 0 PP, Hyper Beam will still be used, and afterwards its current PP will roll over to 63, and full PP ups will be applied to it.
In-game, the target will get to select a move during each turn of Clamp's duration, and will attack your incoming Pokémon with the selected move if you decide to switch before the duration is over.