How to Unlock Darkrai
Darkrai is a Pokémon that can be found in Arceus.
Much like the other Legendaries, you’ll have to beat the game and roll the credits before you can go seeking it out. Once the credits have rolled and you’re into the post-game, you can unlock the Request that will take you straight to it.
Interact with the Blackboard at the Galaxy Team Headquarters in Jubilife Village. There, you should now see a Request titled The Darksome Nightmare. Accept it.
A dialogue will automatically pop up with Cael and once he’s done speaking, you should head to the Coronet Highlands. You’ll want to head for the Clamberclaw Cliffs, but the catch is that it must be night-time. If it’s not already nighttime when you arrive in the Highlands, you can rest at the camp until after dark before heading there.
How to Beat Darkrai
As you can imagine from a post-game Darkrai, this fight isn’t often a walk in the park. You’ll encounter Darkrai at Level 70, so be prepared to have some Pokémon to match. In the post-game, you should have a few Pokémon at a decent enough level to take it on — and the good news is, it’s six against one!
The bad news is, you’ll have to do some dodging first. A special fight is triggered in which Darkrai will attack you in a similar way that the Frenzied Noble Pokémon did. Keep dodging until there’s an opening to throw your Pokémon at it and do battle.
Being a Dark-type Pokémon, you’ll want to have some Bug, Fairy, and Fighting-type moves at the ready. Avoid using Ghost and Psychic-types because even if they’re a slightly higher level, Darkrai is likely able to wipe them out instantly.
Watch out for Darkrai’s Dark Void move, as this will put your Pokémon to sleep and allow it to deal damage. Having items available to cure sleep (like a Full Heal, to be safe) at the ready will help, and you perhaps don’t want to send your best Pokémon out first. Darkrai attacks fast, so you may not have a chance to use a move at all!
Darkrai, unlike Arceus, will not be automatically to your team if you defeat it and will simply leave. To avoid this, make sure you’re whittling Darkrai’s health down to the yellow bar at least — preferably red — and throwing a ball. A Great Ball may not cut it, and a Poké Ball definitely won’t. Use items found later in the game, like an Ultra Ball to get the best result, and make sure you have plenty on hand.
Another good thing to bear in mind is to use status moves to make the Pokémon easier to catch. Using status moves, suchn as paralyzing the Pokémon, can help keep them inside of the Ball. It’s not recommended to use poisoning or burning though, as this will whittle down the Pokémon’s health and if it keeps breaking out of the ball, you may die before you have a chance to catch it.