Detso

Okay so you'll be weak to ice & dragon, so as a result, a steel type could come in handy. Excadrill & Ferrothorn are probably the best choices to use, since Ferrothorn can set up hazards for you in-game or spam leech seed. Excadrill, however, can do amazing in sandstorm, so up to you. This leaves you with the problem of fighting & fire (and ground depending on what you choose), so you could go for Chandelure - it resists absorbs fire and completely resists fighting. Chandelure's main issues are water types, and dark types, so you could use a fighting type that'd take advantage of this, and have coverage you'd not normally have (due to Justified), aka Virizion or Terrakion. Either way, that'll give you a weakness to psychic, so what'sbetter than going with actual dark types? Aaand that brings up the main choices of Krookodile/Scrafty, but beware, Scrafty has a double weakness to fighting, so you could always add in another ghost (since Terrakion is also weak to fighting) to cover this. Either Jellicent or Golurk could work, depending on which you'd prefer. And to finish off, maybe an ice type so you can defeat other dragons w/o being concerned about your future Haxorus?

yeah sure :3 What Pokemon are you considering using?