Hemeon
Iron Ore Pokemon
Steel
level up Eevee while holding (???) in the lowest floor of a deep cavern
The super high pressure environment it lived in caused Eevee's body to condense and harden. The fur it sheds can be woven in with fabrics to create light but sturdy armor.

Alteon
Slipstream Pokemon
Flying
level up Eevee while holding (???) on the highest peak of a high mountain
High in the mountains, the low air pressure causes Eevee to change into Alteon. Its light and airy body can rest on the air and even pass through some thin materials.