The Legendary Trio of Pokémon Black & White are modeled after the Three Musketeers, being justice-bringers that wield sword-like attacks. This makes them all Fighting-types as they're modeled after a fighting style, but each one has its own primary type. Virizion is the Grass-type of the group that swiftly slices foes with its sprout-like horns. Sadly, you can't grow one in Pokémon Sword & Shield. But you can transfer one in. Here's how.
Transferring Virizion From Older Games
Virizion and its brethren are from Gen V, meaning Trainers could first get them on the Nintendo DS. However, the trio also made appearances in two 3DS games as well. Virizion can be caught in Black, White, Black 2, White 2, Omega Ruby, Alpha Sapphire, Ultra Sun, and Ultra Moon.
If you want to bring Virizion to the Nintendo Switch, you'll need the assistance of some apps. First is Pokémon Bank, a 3DS cloud storage app that lets players store Pokémon for $5 a year. If you have it in Black, White, Black 2, or White 2, then you'll need to transfer it to Pokémon Bank using a separate free 3DS app called Poké Transporter. If it's in ORAS or the Sun/Moon series, then it can just be put directly into Pokémon Bank.
Next you need Pokémon Home, a newer cloud storage app that's meant to eventually replace Pokémon Bank. It costs $16 a year on mobile/Switch, and can connect to Bank to facilitate mass migration from the 3DS games. Home will have you put a long code into the 3DS, giving you the ability to transfer Cobalion from Bank to Home. Once Virizion is in Pokémon Home, it can be moved from the cloud into the player's Sword/Shield storage box.
Trading For Virizion On The GTS
Pokémon Home has a function called the GTS that lets Trainers request specific Pokémon trades. If you have extras of a certain Legendary, you could offer it up in exchange for Virizion. Alternatively, you can find a friend with an extra Virizion who is willing to trade.
Transfer From Pokémon GO
Virizion has appeared as a rain in Pokémon GO, so many mobile Trainers have at least one. There are plans to eventually allowed transfer from GO to Home, so this might become an easy avenue to get Virizion into Sword/Shield.
Evolutions & Forms
Virizion cannot evolve or achieve a special Gigantamax form.
What Virizion Does In Battle
Legends say Virizion moves swiftly and slices with leafy blades, so have it do just that. There's a move called Leaf Blade which is perfect for that exact purpose. Aside from that, Virizion can make good use of Sacred Sword, the signature move of the three swords. Virizion can also learn Stone Edge from TMs (or TRs), giving it a good way to deal with those dangerous Fire and Bug types.