Diancie

Diancie is one of the most influential Pokemon in the RU tier, as it possesses phenomenal defensive capabilities and stellar offenses thanks to its good movepool and Fairy typing. With fantastic defensive stats and a decent support movepool, Diancie is able to provide plenty of team support throughout a match, including cleric support with Heal Bell, while holding back dangerous Fire-, Flying-, and Dark-types thanks to its typing. Solid high Base Power STAB moves in Moonblast and Diamond Storm alongside respectable attacking stats also means that Diancie can remove some opposing Pokemon, such as Fletchinder and Sigilyph, quickly before they cause too much trouble. However, providing defensive support isn't the only thing Diancie can do. Diancie even has good coverage moves, such as Earth Power, Psychic, and Hidden Power Fire, allowing it to put good use to a Trick Room sweeper set. Its access to Calm Mind, solid defensive typing, and high defenses also mean it can use a mono-attacking set to slowly wear down and sweep opposing teams. Diancie's fantastic defensive stats are undermined slightly by its low base HP, and a low base Speed stat means Diancie will really only be able to sweep offensively with Trick Room. Diancie's movepool gives it most of the things it wants, but it lacks a strong physical Fairy-type move and special Rock-type move, meaning it usually has to to resort to going mixed for many of its sets. Most importantly, it also lacks a reliable recovery move, reducing its longevity as a defensive stalwart.