The last few generations of Pokemon games have each introduced a new and game-changing battle mechanic to shake up the series. With Pokemon Scarlet and Violet, that mechanic was the terastal phenomenon.
The big selling point for this mechanic is the ability to change a Pokemon's type to any type in the game. This allows defensive and offensive dynamics to change on a dime, and even helps some Pokemon gain more viability. However, it isn’t the first time Game Freak has played around with type-changing mechanics. In fact, there are quite a few ways to change a Pokemon's type, and they’ve been around since the very first games.
9 Soak
Soak is a water type move that was introduced in Pokemon Black and White and is one of the most commonly available type-changing moves in the series. It’s only learnable by water types and certain water-adjacent Pokemon like Azurill and Masquerain.
The move completely transforms the target into a water type. This can completely throw off the strategy of even the strongest Pokemon, but in most cases isn’t really that useful. If a Pokemon is ever released with the proper stats for it though, this could have some great uses as a support move.
8 Forest’s Curse/Trick or Treat
These moves were both introduced together in Pokemon X and Y. They are exclusive to the Trevenant and Gourgeist lines respectively, who are all ghost/grass types. The moves are here together since they both function the same way.
As opposed to Soak, these moves add a type to the target. Forest’s Curse adds the grass type, while Trick or Treat adds the ghost type. This means they are able to create a Pokemon with 3 types, but as novel as that is, the applications are quite niche.
7 Libero/Protean
Libero and Protean are a pair of abilities that function the same, even though they have different names. They are the hidden abilities of Cinderace and Greninja respectively. Both will change the user’s type to match the move they are about to use, allowing them to always get a same-type attack bonus(STAB).
From generations 6-8, these were powerful abilities that made their users powerful offensive threats, Greninja especially. However, as of Scarlet and Violet, these abilities have been nerfed, and will only allow a type change 1 time until the user switches out.
6 Color Change
Color Change can be considered the predecessor to abilities like Libero and Protean, and is the first type-changing ability introduced into the series. It is the signature ability of Kecleon, and has remained exclusive to it.
This ability functions as the opposite of Libero, changing its user’s type to the type of the last move to hit it. While this provides some utility due to most types resisting themselves, this can be easily exploited, since the opponent controls Kecleon’s type changes and can plan around them.
5 Double Shock/Burn Up
Despite these moves functioning identically, they were released separately, with Double Shock being brand new to Scarlet and Violet, while Burn Up debuted in Pokemon Sun and Moon. They can only be used by Pokemon of the corresponding type.
Both moves are extremely powerful, with a base power of 120 and 130 respectively. For comparison, most attacking moves used in competitive Pokemon hover around 80-100 base power. However, upon use, these moves rob their user of the electric or fire type respectively, meaning they are one-use moves.
4 Roost
Roost is an extremely useful move that is a mainstay in both casual and competitive Pokemon. It’s a flying type move that allows the user to recover up to 50% of their health. Recovery moves of this strength are few and far between, so this is a big boon for flying types.
A feature of the move that some players are unaware of, is that after using it, the user loses the flying type for the rest of the turn. On slower Pokemon, this might not make a difference, but faster Pokemon can survive hits they otherwise wouldn’t by removing their own flying type before their opponent can attack.
3 Conversion
This is the first of the two Conversion moves. Conversion is exclusive to the Porygon evolution line, and was introduced all the way back in Pokemon Red and Blue, making it the first type-altering move in the series.
When used, it changes the user’s type to match the first move in their move list. This is a very flexible way to alter a Pokemon's type, but due to the Porygon line’s limited moveset, there are only so many types this can actually transform them into.
2 Conversion 2
Fittingly, Conversion 2 was introduced in the 2nd generation of games, starting with Pokemon Gold and Silver. It is also exclusive to the Porygon line. As opposed to Conversion, this move changes the user’s type to a type that resists the last move it was hit by.
In practice, it’s a better version of Kecleon’s Color Change ability, and is more unpredictable, since several types resist any given type. However, this same randomness makes it unreliable, so it’s not really worth using in most scenarios.
1 Reflect Type
Introduced in Pokemon Black and White, Reflect Type is a move that functions somewhat similarly to Ditto's transform ability. It has been learnable by a few Pokemon over the years, but most often appears on Mew’s moveset.
When used, Reflect Type fittingly reflects the target's type, making its user the same type as them. So, for instance, using it against a Blastoise would make the user a water type. This has limited application, as most Pokemon resist themselves, but it doesn’t see much use outside niche strategies.