Skarmory
Rocky Helmet
Ability: Sturdy
Level: 50
EVs: 252 HP/ 132 Atk/ 124 Def
Impish Nature
- Brave Bird
- Roost
- Iron Defense
- Toxic
Take the EVs with a grain of salt. I made a Skarmory set for a team a while ago but didn't save it anywhere. I think this is it, and after a few calcs it seems alright. Max Def still gets 2HKOd by unboosted Lucario's CC without boosts, and the Atk OHKOs Mega Blaziken(not part of this core, but an important target nonetheless. What I don't get is why the Atk is so much-a little less would still guarantee an OHKO on Blazi.)
Toxic takes out Hippo, which can't really do anything but Yawn with the moves it normally uses, and Skarmory can definitely wait out the sleep turns after an ID if this core is the oppo' whole team. It's also the best option vs DNite, though only after you've used ID in case it's Fire Punch(Fire Blast is extremely rare, and Skarms will definitely live it from full cause Sturdy. Plus there's at 15% chance for it to miss.)
Stalling out Lucario's and DNite with ID while they break themselves on your helmet is usually fine. DNite is only boosting Atk one stage with DD to your two stage ID boost, though SD Lucario's is kind of a problem. It's also worth noting that more Lucario's tend to go physical, which is important since special variants are much more dangerous.
Here are some calcs.
252 Atk Adaptability Mega Lucario Close Combat vs. 252 HP / 124+ Def Skarmory: 92-110 (53.4 - 63.9%) -- guaranteed 2HKO
132 Atk Skarmory Brave Bird vs. 0 HP / 0 Def Mega Lucario: 75-88 (51.7 - 60.6%) -- guaranteed 2HKO
Pretty crazy how much it takes from BB. If you already have +2 Def you can just ID on Lucario. If it uses Close Combat it'll take helmet damage and lower its Def. After a BB from Skarm on a -1 Def Luc it only really needs another round of helmet damage to die, and in the meantime Skarm can Roost or use ID again. The damage Luc does to unboosted Skarms is pretty high so you'd want another answer to it on your team, but even in the worst of times Skarm can just take the CC, then BB on the -1 Luc, and then Luc finishes you next turn, but that's after taking so much damage its dead or close, and anything with Extremespeed could then come in and revenge the weakened Luc.
4 Atk Hippowdon Earthquake vs. 252 HP / 124+ Def Skarmory: 80-96 (46.5 - 55.8%) -- 64.8% chance to 2HKO
Not that bad at all, and it only applies if you're Roosting, Gravity is in effect...or you've been Trucked an Iron Ball. Even in those weird situations it doesn't matter since you just boost your Def then Roost. There aren't any other offensive calcs that are at all relevant. The bottom line is Skarms uses Toxic on Hippo but is immune to poison itself.
252+ Atk Choice Band Dragonite Fire Punch vs. 252 HP / 124+ Def Skarmory: 180-216 (104.6 - 125.5%) -- guaranteed OHKO
252+ Atk Choice Band Dragonite Superpower vs. 252 HP / 124+ Def Skarmory: 72-85 (41.8 - 49.4%) -- guaranteed 3HKO
+2 252+ Atk Dragonite Outrage vs. 252 HP / 124+ Def Skarmory: 72-84 (41.8 - 48.8%) -- guaranteed 3HKO
Short version is that Fire Punch is the only way DNite does anything, aside from the extremely rare Fire Blast or even rarer Thunderpunch and Thunderbolt, and only if Skarms isn't boosted. Skarms won't do much damage with BB(guaranteed 4HKO,) but has Toxic and makes DNite take helmet damage.