ummm built this in like 5 minutes!!!
My brain immediately went to Spikes b/c Rhyperior is infamously great at threatening common removal options in Salamence, Mandibuzz, Moltres, and Rotom-Heat (former two don't like running it but they're both blanked by it anyways). Skarmory was the obvious choice for Spikes; also checks Scizor and appreciates Rhyperior being able to handle Celesteela pretty well, as well as threatening the aforementioned forms of hazard removal. Dhelmise gives me removal without removing my own hazards, counterplay vs bulky Water-types like Rotom-Wash, Keldeo, Primarina, etc, and similarly appreciates Rhyperior threatening Flying-types, mainly Mandibuzz and Salamence. Azelf w/ Knock makes it much easier to abuse Mandibuzz and Chansey, and also gives me indirect counterplay to SD Cobalion, which has the potential to walk all over this build otherwise. Primarina is just the standard glue for this team; checks Hydreigon, makes it even harder for hazard removal to safely click Rapid Spin/Defog with this in the back, and synergizes with Heat Crash Rhyperior, in that Rhyperior baits Grass-types, which makes Primarina much more potent defensively. Rotom was honestly something I
kinda slapped on here. Nonetheless, I think it's still good here for its ability to clean vs teams that have Swampert/Hydreigon/Nihilego weakened, as well as being another Scizor answer, which is never bad to have.