Protean

Protean transforms its bearer into a dynamic type-shifting powerhouse by changing their type to match each move they use, with the transformation occurring just before the move is executed. This timing is crucial as it allows the Pokemon to gain Same Type Attack Bonus (STAB) on every move in their arsenal, effectively boosting all attacks by 50% damage. The ability also provides defensive utility by potentially changing resistances and weaknesses mid-battle, making the Pokemon unpredictable and harder to counter.

The ability underwent a significant nerf in Generation 9, where it now only activates once per battle entry rather than on every move. This change dramatically reduced its competitive impact, transforming it from one of the most powerful abilities in the game to a more situational tool. In earlier generations, Pokemon like Greninja became notorious for their versatility, able to use moves like Ice Beam, U-turn, or Hidden Power while gaining STAB on each attack and constantly shifting their defensive profile.

Despite the Generation 9 limitation, Protean remains valuable for securing crucial KOs or surviving specific attacks when used strategically. The ability works with any damaging or status move, making it particularly effective on Pokemon with diverse movepools. Kecleon was the original bearer, though Greninja popularized the ability's competitive potential before the restriction was implemented.