As you people probably know, Eevee, and only Eevee, gets a Z-move called Extreme Evoboost. I was bored and decided to come up with a set to make it work:
Eevee @ (Eevee Z Crystal)
Ability: Adaptability
EVs: 252 HP/ 4 Def/ 252 Spe
Jolly Nature
*Extreme EvoBoost
- Baton Pass
- Protect/Refresh
- Wish
- Return
Stats at Lv. 50 (Stats at +2)
HP 162
Atk 75 (150)
Def 71 (142)
SpA 58 (116)
SpD 85 (170)
Spe 117 (234) vs Jolly Choice Scarf Landorus T (235)
Extreme EvoBoost and Baton Pass are the main reasons for using this set, since passing along two Ancient Power boosts to something actually able to use them can be devastating. Protect is used to scout for moves, particularly anything super-effective or otherwise strong on a faster opponent. Refresh can be used instead to remove confusion etc., which Baton Pass transfers (although non-volatile status like burn is not passed along, so Protect is probably better). Wish is recovery, and can also be passed along to other Pokémon on your team if your Baton Pass recipient is injured. Finally, Return is a backup STAB attack for emergencies.
The EVs are designed to bulk Eevee up as well as let it get EvoBoost off as quickly as possible. Once it does so, its better stats should hold up to attacks as long as needed. We have to use a Z crystal, otherwise Eevee can't use this move. Jolly is used to get Eevee's speed up some whilst lowering its unused Special Attack. Adaptability lets Return hit harder in the event that Eevee needs to use this move.