Aegislash (Leftovers)
Ability: Stance Change
EVs: 4 Def / 252 Atk / 252 SpD
Adamant Nature
- King's Shield
- Swords Dance
- Sacred Sword
- Iron Head
While 2 set up moves and 2 attacking moves might seem gimmicky, Aegislash is probably the only mon that could pull it off. King's Shield acts like protect and reduces the user's Attack. With its amazing 150 SpD and Def, Aegislash can stay in Shield Forme and use Swords Dance at least once, if not twice, while using King's Shield in between if the opponent is a Attacker. After two turns of set up, Aegislash becomes an Uber-level threat. Stance Change switches its Def and Attack, sure, but there's always King's Shield to cover for incoming Physical Attacks. I'm guessing Aegislash will be OU this gen.
First, you should max out HP, not SpD. Aegislash has much lower HP than SpD and thus benefits much more by investing in HP. Second, i don't think that a Swords Dance + King's Shield is going to be really good. No matter what two attacking moves you use (Shadow Sneak + Iron Head, Shadow Sneak + Sacred Sword, Iron Head + Sacred Sword), Keldeo, Garchomp, Landorus-T, Tentacruel, Politoed, Rotom-W, Volcarona, Ninetales, and Skarmory all switch into you easily and either KO you, threaten with status (Scald and WoW), or phaze while taking almost no damage (Skarmory). And of 'course, each two move combo has its own extra checks. Iron Head + Shadow Sneak is an invite to Heatran and Ferrothorn, Iron Head + Sacred Sword allows Starmie, Jellicent, and Thundurus-T to switch into you easily, and lastly, Shadow Sneak + Sacred Sword is not checked by anything extra, but lacks immediate power, with its strongest move being an unSTABed 90 BP move. And all those are the counters. Anything offensive that can take a +2 Shadow Sneak will probably OHKO back, as it will attack Aegishield's weak defenses (60 / 60 / 60), making for a huge list of checks.
So, instead of trying to make a Pokemon with 60 base Speed a sweeper, i think that this Pokemon should be better used as a typical defensive Ghost with an extra gimmick added to the mix in the form of Stance Change. Assuming Aegishield gets Pain Split and WoW, and that those two moves activate the Defense Forme, i think the most viable sets would be WoW, Pain Split, and any of Iron Head, Shadow Sneak, and Sacred Sword in the last two slots, with either a tankish 252 HP / 252 Atk Adamant spread, or a more passive 252 HP / 252 Def+ or 252 SpD spread (or any spread between those two really), with Lefties on both sets. Aegishield's advantage over other defensive Pokemon is that it can hit back insanely hard, and its advantage over other tankish Pokemon is that it has huge mixed defenses, giving it an edge over both. It will be able to take a hit from a threatening attacker, and either burn it, OHKO it (or 2HKO it with Shadow Sneak), or use Pain Split + Shadow Sneak to take it down, and all this without getting his weaker defenses exposed. After it has done its job, it can simply switch out and revert back to Defense form, and come back again whenever its needed again. For example let's take a set with 252 HP / 156 Atk / 100 SpD+, Leftovers, and a moveset of WoW / Pain Split / Iron Head / Shadow Sneak and see how it fares against some offensive Pokemon:
- 252 SpA Life Orb Starmie Hydro Pump vs. 252 HP / 100+ SpD Aegislash: 126-149 (38.88 - 45.98%) -- guaranteed 3HKO after Stealth Rock.
Against offensive Starmie, Aegislash uses Pain Split in the first turn and not Shadow Sneak in order to not activate the Attack Forme and get OHKOed by Hydro Pump after and in case Starmie switches out. In the next turn, Aegislash can finish Starmie off with Shadow Sneak, which does 60.53 - 72.03%, enough to OHKO after Pain Split.
- +2 252 Atk Rock Gem Terrakion Stone Edge vs. 252 HP / 0 Def Aegislash: 171-201 (52.77 - 62.03%) -- guaranteed 2HKO after Stealth Rock
Just take the hit and OHKO back with Iron Head, which does 83.33 - 98.14%, or finish Terrakion off with a Shadow Sneak if it survives.
- +2 252+ Atk Flying Gem Scizor Acrobatics (110 BP) vs. 252 HP / 0 Def Aegislash: 138-163 (42.59 - 50.3%) -- 1.95% chance to 2HKO after Stealth Rock
Take the hit and WoW him. Then use Pain Split and if he stays in slowly kill him with Iron Head.
- 252 SpA Choice Specs Latios Hidden Power Fire vs. 252 HP / 136+ SpD Aegislash: 114-136 (35.18 - 41.97%) -- guaranteed 3HKO after Stealth Rock
You avoid the 2HKO no matter what, and using Pain Split is the best option. If Latios attacks again, you heal back with Pain Split and finish him off with Shadow Sneak in the next turn. If he switches out you just heal and switch out the next turn.
Those are just some examples to showcase how i think that Aegislash would be played, and seeing how i have made quite a bit of assumptions take it with a grain of salt...