Houndour can be caught in Altering Cave.
The only place in-game for Houndour is in the Altering Cave, but you have to do something to make it appear. Other than that, you must trade or cheat.
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You can catch a Houndour in the Altering Cave in Pokemon FireRed.
Since you can't catch houndour your going to have to trade the Pokemon colosseum houndoom to firered breed it then hatch the egg to get houndour or you can get one from emerald's safari zone.
You get a houndour then evolve it i will update when I find out where to catch houndour
Houndour can't be caught in firered so get one from emerald or colosseum.
You catch Houndour at night on route 7 in kanto