Pokémon GO trainers who played GO Fest 2020 this past weekend were awarded with a quest that led to encounters with four Shadow Legendary Pokémon, as well as the Mythical Pokémon Victini. The Legendaries included the trio of Kanto Birds (Articuno, Zapdos, and Moltres) which had been obtainable in the past as Shadow Pokémon from Giovanni… as well as the first ever release of Shadow Mewtwo. Shadow Pokémon have essentially had a darkness placed upon them by Team GO Rocket that makes them strike harder and take more damage: a function in the game called "Shadow Boost." All Shadow Pokémon have a button on their page in Pokémon storage called "Purify," allowing trainers to remove the Shadow that Team GO Rocket has put upon them. What, though, does this do, and should you purify your Shadow Mewtwo?
Should you Purify Shadow Mewtwo?
Under no circumstances, no.
Shadow Mewtwo is disproportionately stronger than its normal form, and here's why. A Pokémon's IVs, the "individual values," is the base metric by which trainers understand the potential a Pokémon can have. IVs can add points of value to the base attack, defense, and HP of a Pokémon species. Shadow Boost, however, boosts the Pokémon's overall damage output by 20%. This means even with the lowest IVs a trainer's encounterable Shadow Mewtwo could have been coded with at GO Fest 2020, it will hit harder than a 100% IV standard Mewtwo. Shadow Pokémon take more damage than the standard Pokémon, yes, but since raid battles are based on how much damage can be done to the Raid Boss in the shortest period of time, attack is prioritized over defense, making Shadow Pokémon reign supreme.
When it comes to any Pokémon, when asking yourself if you should purify it, here is the basic answer: If this Pokémon already functions well in raids, the Shadow form functions better.
What does Purification do?
Purification will essentially turn a Shadow Pokémon into its standard form, with the added bonus of that Pokémon being cheaper to power up. It also increases each IV by two points, which would turn, for example, a Shadow Mewtwo with a score of thirteen IV points in attack, defense, and HP into a 100% Mewtwo. However, the Shadow Boost is lost. Until Niantic offers a boost to Purified Pokémon beyond what already exists, there is no benefit to the function.
What is special about GO Fest 2020's Shadow Mewtwo?
Normally, Shadow Pokémon encountered at the end of Team GO Rocket battles do not have an IV-floor. This means that they are like wild Pokémon, in that trainers have the same odds of encountering a 0% Shadow Pokémon as they do a 100%. For example, this is the IV breakdown of Shadow Legendary Pokémon that I personally received pre-GO Fest 2020, with the general note that IVs can range from zero to fifteen:
- SHADOW ARTICUNO: 5/13/4
- SHADOW ZAPDOS: 13/8/15
- SHADOW MOLTRES: 7/14/12
Normally, Legendary Pokémon are caught in Raids and Special Research, all of which have a floor of IVs that prevent catches from being lower than 10/10/10. This is notable because, for the first time, Shadow Legendary Pokémon were available at GO Fest 2020 not through the encounter at the end of a Team GO Rocket battle, but through Special Research. This gave them the 10/10/10 IV floor, essentially guaranteeing encounters with four Pokémon that are stronger than their 100% equivalent. Here's the Shadow Mewtwo and Bird trio breakdown I received from GO Fest 2020:
- SHADOW ARTICUNO: 15/12/14
- SHADOW ZAPDOS: 13/14/11
- SHADOW MOLTRES: 10/14/14
- SHADOW MEWTWO: 10/10/10
Essentially, the GO Fest 2020 Shadow Mewtwo above is the lowest IV version of the Pokémon that could be encountered, and it still hits much harder than the 100% IV standard Mewtwo.
So until Niantic changes the function of Purification, the answer is simple: No. You do not want to purify your Shadow Pokémon.