Magikarp is the headliner, funnily enough
Game Freak has been cycling raid events in and out for Pokemon Sword and Shield, and it looks like they are going to be following that schedule throughout 2020.
A new Wild Area event is in the works, and it’s live right now through January 3 at 7PM ET. More Magikarps are going to show up in the Wild Area at all raid dens, which is extremely lame at face value: but there’s a catch. This event focuses on shiny Magikarp, just in case your full Pokedex Shiny Charm isn’t working well. You can also throw Wishing Pieces into dens if one isn’t spawning for you.
Anecdotally, the spawn rate for a shiny Magikarp is pretty high, so get going in the next few days if you want one! As a reminder, the Gigantamax Snorlax event is still happening, as is the Butterfree event. Both of those will be ending soon as they have an “early January” expiration date.
Max Raid Battle Event [Serebii.net]