Poison-types: I have to agree with David0895, dealing with Heatran and being checked by things like Mollux and Plasmanta is kinda contradictory, as they require similar coverage.
I just want to point out that Heatran is capable of being hit by fighting coverage, and while this doesn't pair well with blacephalon in the coverage department Blacephalon takes a crap ton from a moonblast coming of sizeable power + stealth rock. As well as this Plasmanta can still be seen as a check, as plasmanta can come in on Cap24's stabs and pressure us out if we are slower(given environmental scenarios).