Maxfnd

So I've already decided what team i want for my playthrough and one of those is houndour, obviously and i was trying to find out how to get one but i'm getting lots of mixed ideas on how you actually catch one, Can someone please clarify if houdour is simply a wild encounter in the magma alley or if it's a special event that occurs under certain circumstances, and if it is a special event, how exactly do i get it to occur?. I'm up to fighting shelly if that helps with anything, thanks in advance