Counter dealing all of an enemy Rhydon that uses Horn Drill and missed's HP.
The Horn Drill and Fissure glitch is a glitch in Pokémon Gold, Silver and Crystal, which causes the move Counter to deal damage, (believed to be 'infinite') when Horn Drill or Fissure is used by another Pokémon and misses, and when the user of Horn Drill or Fissure is of the same level or a higher level than the user.
This is considered a glitch because in Pokémon Stadium 2 this behavior no longer occurs. Additionally, the glitch does not work with Guillotine.
Counter will always miss if Guillotine was used, even if an X Accuracy was used (X Accuracy maximizes accuracy in Generation I and II).
This is presumably the 'normal' behavior for a move that cannot be countered. For example, if the opponent used Surf (a special move) or Swords Dance (a non-damaging move), Counter would also miss.
If the enemy Pokémon was of a lower level than the user, Horn Drill will not affect the user, and using Counter will cause Counter to always miss, even if an X Accuracy was used.
- A Pokémon that knows either Horn Drill/Fissure or Counter.
- The Horn Drill/Fissure user has to be of the same level as the opponent, or of a higher level, but not too much higher or the move will be likely to hit (see here for more information).
- The Counter Pokémon must be able to be affected by Horn Drill or Fissure (i.e. it mustn't be a Ghost or Flying type, respectively)
- Another Pokémon that the above will fight, which knows either Horn Drill or Counter (whichever the other one doesn't know.)
- Have Horn Drill/Fissure and Counter be used by the Pokémon in the same turn, and have Horn Drill miss.
- The Counter using Pokémon will deal damage to its opponent.