I featured Cian Maher a while ago when he claimed the Gen 2 Pokédex was the best. Now he’s back with mathematical evidence that we need a Ground or Poison type Eeveelution. Fundamentally, the calculations involve checking how the remaining non-Eeveelution types fair against the current Eeveelution types. Ground and Poison won out. Cian also looked at the effect either one would have on the meta:
Ground and Poison-type Eeveelutions could check Steel-types and Fairy-types, respectively, both of which are arguably the strongest single types in the game right now. It would be nice to see one of Eevee’s various forms carving itself out a spot in the modern metagame.
To conclude: The next Eeveelution should be Ground-type, followed closely by a Poison-type. Popular fan names for these types include Terreon and Toxeon. We reckon they sound alright.