There is no such TM called horn drill.
Chat with our AI personalities
Horn drill is not a TM in diamond only in red and blue.
Unfortunately, Nidoking doesn't learn Horn Drill at all. In order to have your Nidoking learn Horn Drill, you'll need to level up your Nidorino to level 46 (you learn Horn Drill at that level) and then evolve it into a Nidoking.
Look bub, i think you might teach it a TM i don't know, or it just might learn it by a level.
get rhydon to lvl 38
Lots. Earthquake, horn drill, mega kick etc...