Abomasnow @ Choice Band/Lum Berry
Ability: Soundproof
Tera Type: Ground/Fire
EVs: 168 HP / 252 Atk / 88 Spe
Adamant Nature
- Wood Hammer
- Ice Spinner
- Leech Seed/Tera Blast/Ice Shard
- Earthquake
252+ Atk Choice Band Tera Ground Abomasnow Earthquake vs. 248 HP / 0 Def Skeledirge: 422-500 (102.6 - 121.6%) -- guaranteed OHKO
A Skeledirge with 248 HP and 0 Defense that has yet to Tera cannot switch into the Choice Band variant at all if they don't already know the EQ is coming (unless you've revealed it before they won't, because when was the last time you came across a physical Abomasnow anywhere above the 1300s?).
Should it already have it's type changed or ignoring the fact we only need to base ourselves only on the set we were given, here's me going on a few different tangents on how these Tera Ground with Lum Berry/Tera Fire with CB sets could also beat (probably) EVERY Skeledirge imaginable. If it doesn't outright die, the team it's on takes a hit from forcing Tera. Here's all the potential scenarios!
So, because not every Skeledirge will be rocking full SpDef as it's physical wall capabilities are still quite good and there's other answers to Espahtra and Iron Moth, you might run into one against this set and it will live the initial EQ even with CB and Tera Ground, though just barely:
252+ Atk Choice Band Tera Ground Abomasnow Earthquake vs. 248 HP / 252 Def Skeledirge: 336-396 (81.7 - 96.3%) -- guaranteed 2HKO
Unless it's running more than 40 Speed EVs (faster than base 70), Abomasnow gets the jump on the opponent via it's own Speed investment. Either way, when was the last time you saw a Skeledirge with more speed investment than for outspeeding the base 70s?
Anyway, we'll go explore the other also reliable variants: CB Tera Fire and Lum Berry Tera Ground. Because they beat the SpDef sets anyway like the one above, i'll only be talking vs PhysDef dirge from here forward.
As for Banded Tera Fire, Skeledirge always gets 2HKO'd by Earthquake:
252+ Atk Choice Band Abomasnow Earthquake vs. 248 HP / 252 Def Skeledirge: 224-264 (54.5 - 64.2%) -- guaranteed 2HKO
So, there's 3 ways to respond to it:
1) Kill Abomasnow before it kills you. Torch Song is the go-to, i mean, why wouldn't you click it? Not only are you faster, but Abomasnow is 4x weak to it. Skeledirge simply wins the exchange...right? Wrong. So, so wrong. Thanks to it's 72 Speed EVs, it always outspeeds 20 Speed EVs Skeledirge. And i only included this weird investment for the sake of it, i've no idea what it's supposed to outspeed like that (too much for Corviknight, too little for the base 70s). Well... what if it's faster anyway? See, here's something neat about Abomasnow, something you probably didn't even know before reading this. It's hidden ability is Soundproof, making sound-based moves do 0 damage. Torch Song, as the name implies, is a sound move, making our chilly friend completely immune to it. If you go for the kill, Abomasnow immediately wins, since not only your 2 options are Hex (22.8 - 26.8%) or the much less common Earth Power who doesn't even nail a 2HKO (given no unlucky SpD drop) but also consider Abomasnow outspeeds Dirge. We always win the scenario no matter what.
2) Tera and use Will-O-Wisp. While this WOULD work in theory, in practice you have your own Terastalization in the back. Tera Fire on the CB set assures that you can't get burnt at all. Even though you outspeed it anyway and will kill it before it gets a chance to move.
3) Tera and use Slack Off. Sadly we can't do much about this one, but remember what we're here to do: pave the way for our sweeper teammates to wreck the opponent thanks to Skeledirge not being able to wall them anymore. And for some sweepers, this has already been accomplished; forcing a Tera means Skeledirge won't be able to tank Volcarona or Iron Moth's STABs as it used to.
As for the Tera Ground Lum Berry set, I'd say it's even better off. It gets the same damage output as Choice Band with the extra of not needing to be choice locked while reaping the benefit of Will-O-Wisp immunity thanks to it's item.
This means that Skeledirge's options nº 1) and 2) still net you a win against it, but now you can also still thwart it even more on nº 3). Thanks to not being choice locked, the enemy Skeledirge's prone to eat a Leech Seed, which not only ensures we can threaten a slim chance of a 2HKO or the reliable 3HKO which can burn more Slack Off PP while already having forced a desperate lose-lose Terastalize. Yet another bonus: the somewhat uncommon Tera Water dirge gets threatened really hard by Wood Hammer to the point where it cannot possibly live after a super-effective EQ and another regular one, even if it recovers back some damage, since:
252+ Atk Abomasnow Wood Hammer vs. 248 HP / 252 Def Tera Water Skeledirge: 270-318 (65.6 - 77.3%) -- guaranteed 2HKO
So, like i said, i think Lum Berry Tera Ground does even better than CB Tera Fire against every Skeledirge.
The rest of the moves are just for generally getting some offensive utility outside of this specific 1v1, even though it's not actually required i think it'd have been a nice touch.
Overall, can't really go wrong with these 3 sets