So let's start with this Mimikyu set.
Mimikyu @ Life Orb
Ability: Disguise
EVs: 252 Atk / 4 SpD / 252 Spe
Jolly Nature
- Swords Dance
- Play Rough
- Shadow Sneak
- Drain Punch
Now, let's say we wanted to make it able to abuse priority. Well, we can do that here!
Fortemons (Mimikyu) @ Shadow Sneak
Ability: Disguise
EVs: 252 Atk / 4 SpD / 252 Spe
Jolly Nature
- Swords Dance
- Play Rough
- Shadow Sneak
- Drain Punch
By naming the Mimikyu "Fortemons", we made it able to use Fortemons' mechanics, thus allowing it to get +1 priority on all of it's attacks by having Shadow Sneak as it's item.
Now, let's take a defensive Landorus-Therian.
Landorus-Therian @ Leftovers
Ability: Intimidate
EVs: 252 HP / 240 Def / 16 Spe
Impish Nature
- Stealth Rock
- Earthquake
- Hidden Power Ice
- U-turn
There is a lot that could be improved upon here. However, we can make those improvements.
STABmons (Landorus-Therian) @ Flyinium Z
Ability: Intimidate
EVs: 252 Atk / 240 Def / 16 Spe
Adamant Nature
- Stealth Rock
- Earthquake
- Beak Blast
- U-turn
Now it actually has Flying-type STAB, and a way to inflict status.
But we could do better...
STABmons (Landorus-Therian) @ Flyinium Z
Ability: Intimidate
EVs: 252 Atk / 240 Def / 16 Spe
Adamant Nature
- Stealth Rock
- Thousand Arrows
- Beak Blast
- U-turn
...If Thousand Arrows wasn't restricted in STABmons.
You may also think of having a certain someone on your team...
Balanced Hackmons (Chansey) @ Eviolite
Ability: Imposter
- pretty much anything
...but use of Balanced Hackmons is banned, so no Imposter Chansey for you.