Type: Null is a unique Legendary Pokémon that first appeared in Generation VII, the Pokémon Sun and Moon games. Its in-game lore dictates that it was created by the Aether Foundation to fend off the Ultra Beasts, and is a unique Legendary Pokémon in that it evolves. Here's everything you need to know about evolving Type: Null in the newer generation games: Pokémon Sword and Shield.
How to Evolve Type: Null in Pokémon Sword and Shield
Type: Null evolves into the Legendary Pokémon Silvally, which is additionally unique in that it can change what typing it is based on which type of memory item it is holding. Because of Type: Null's background of being used by the evil Aether Foundation, it only is able to evolve when leveling up with maximum friendship of 220. This is true in both its original appearances in Pokémon Sun and Moon, and well as its current appearance in Pokémon Sword and Shield.
Although you can obtain Type: Null through the story of Pokémon Sun and Moon, you cannot do the same in Pokémon Sword and Shield. Fortunately, unlike many other post-game Legendary Pokémon, you do not have to finish a tedious grind or puzzle before chucking 30 Ultra Balls at it. Type: Null will be given to you, if you know where to go. Speaking towards the character standing next to a Type: Null on the left of the Pokémon Sword and Shield Battle Tower will result in you receiving Type: Null.
Once you have Type: Null, make sure to max out its Friendship stat by feeding and playing with it in the Pokémon Camp, level it up, and you'll have yourself Silvally, and be one step closer to completing the Sword and Shield National Dex.