Okay so I don't really like starting off with non-standard sets when building teams, at least not in the current metagame since it's very developed. Most of the time, they're non-standard because they're not that good, so at least in my experience, building around them tends to produce teams that are flimsy, inconsistent, and not that fun to use. Jox will heavily disagree with that, but he's a squirtle so I don't value his opinion whatsoever. This isn't to say that I don't use them at all, as some of the better non-standard sets definitely have their own niche, so even though they're not good, they may still fit onto a good team quite well. In this case, I decided to work with a pretty standard offensive core in gastbra. Gastly ended up being the fairium set because it's best able to pressure timburr, vullaby, and mienfoo, as they can be pretty rough for the rest of the team to break, and timburr/slowfoo remain big threats even if they're heavily weakened so it's nice to be able to cleanly ohko them versus lo psychic. The HP investment lets me pose as a subwow set so the fighters are less inclined to immediately switch out after my first sub. I chose Abra as my designated HP fire user, which is needed considering how all four of my sweepers can't immediately break it otherwise. I feel that one HP fire user is enough because ferro is pretty easy to wear down for the team. Psychic terrain gives abra the opportunity to sweep late game and also supports carvanha.

The usual way to support this core against grimer, pawniard, magnemite, and so on is to run trapinch or diglett to trap them, but I decided to go with a sand core to pressure them offensively instead (while also getting my rock setter in). This was honestly mostly to satisfy the requirement for an underrated mon, but lo sand rush drilbur offers two pretty sweet points over trappers: a) it's a lot consistently stronger, which makes it better for pressuring vullaby in particular on top of generally bulky mons like ferro/mudbray; and b) it can act as a safety net against smashers and weak armor mons, easing the pressure off of sashbra so that I can save it for a late game sweep more often. Hippopotas is a physically defensive spread to let it more reliably handle a lot of things I don't really have switchins for or would have to waste ferro on, like onix/mudbray/fire punch burr. Toxic is mainly to make it a lot easier to chip vullaby into range of my other mons, as opposed to just popping weak armor with rock slide and forcing me to blow abra's sash or sack things to get drilbur in with sand. I could run spin for drilbur's last slot, but gastly/sand rush burr/carv is usually enough against webs, and I'm fine with attempting to just outmuscle opposing hazard stack. Substitute helps with dodging sucker/spore, punishing weakened foo trying to fake out into a sack, and generally easing prediction. It does stall out sand turns, but lo dril is still a pretty big threat outside of sand.

Drilbur being able to revenge-kill various sweepers means that I don't have to go for the bulky voltturn core to check those sweepers that usually rounds out gastbra teams, so I went for full ho instead with carvanha + ferro. Not having voltturn does make it harder for gastbra/carv to get into play, but ideally hazard stacking + strong offensive threats will mean that by the time I run out of sacks, the opposing team will be weakened enough for abra or carv to clean. I went with a faster ferro spread with explosion (the evs still hit evio numbers and stuff) to preserve hazards after paralyzing vully switchins, weaken timburr/foo heavily, and generally gain momentum. I chose carv over another sweeper here because I like that it can immediately begin to break without compromising its clean unlike, say, smashers or scrag, so that it can still put in work when it's not my wincon; and it's usually more threatening to opposing ho than other mons that can do this, mainly snivy, where abra/drilbur can cover slower teams that snivy might fare better against.