An Impish Nature raises Defense and lowers Special Attack. Because your Impish Run Away Eevee has good IVs in all defensive stats, try making it a Vaporeon. Vaporeon is a great tank, and while Special Attack is helpful for one, it isn't necessary -- Wish + Protect is still viable.
Vaporeon @ Leftovers
Ability: Water Absorb
EVs: 252 HP / 252 Def or SpD / 4 SpA
Impish Nature
- Wish
- Protect
- Scald
- Shadow Ball / Yawn / Charm
A Sassy Nature raises Special Defense and lowers Speed. The most specially bulky Eeveelution is Sylveon, which can function as an effective special wall with its IVs and a Sassy Nature. It also doesn't exist in these games (ILCA why), so try either another Vaporeon, or Glaceon, which can do with a bit of extra bulk.
Glaceon @ Leftovers
Ability: Snow Cloak
EVs: 252 SpA / 252 SpD / 4 HP
Sassy Nature
- Freeze-Dry / Ice Beam
- Shadow Ball
- Wish
- Protect
Congrats on the shinies!