Protean (Ability)

Protean is a rare and hidden ability held by certain animals.

In Battle Use
Animals with the Protean ability change their overall typing to whatever typing the move they use within a battle. This provides additional STAB power into their moves.

Speculation
This ability appears to be similar to adaptation and various techniques such as camouflaging in which animals would change their overall characteristics and body composition in favour for an advantage in battle.