Many people have had the opportunity to catch Lugia or Articuno at this point, but to actually get the ball to go grey is a completely different story. Lugia has a base catch percentage of 2% per throw, while Articuno is a little over 3%. That means that 2 of every 100 balls at Lugia will end in a catch and about 3 of every 100 will catch Articuno. There are some ways to improve your odds, but it’s still very difficult.
These percentages increase with every single throw. If you manage to get 10 throws at Lugia, your percentage on the last ball will be 20%, which still isn’t great. If you really want to increase chances, you have to land curveballs. A curveball gives you a 2x multiplier on your throws, which will make 10 curveball throws equal 40%, rather than 20%.
It’s also important to use Golden Razzberries. These give you a huge advantage with each throw and help raise your catch percentage. It’s better to do some lesser raids to farm these up before attempting a Legendary, but if you can perfect your curveballs, feed the Legendary a bunch of Golden Razzberries, and be persistent, you can walk away with a catch. It won’t be easy at all, but if you dedicate enough time to it, you’ll be the proud owner of a Lugia and Articuno forever.