40 HP, 216 Def, 252 Sp. Attack
- Calm Mind
- Hidden Power Fire/Moonblast
Calm Mind makes Cresselia a very powerful and dangerous Pokemon. She's already very bulky and Calm Mind both heightens that and helps her gain the offense she needs to tank through most of a team. Even with 252 Sp. Attack EVs, Cresselia still has better physical defense than many physical walls, and will remain a solid choice as a defensive member of your team. The remaining 256 EVs are invested to specifically maximize physical defense as efficiently as possible; Basically, going max HP or max Defense, or any combination in-between won't give you more physical bulk than the EVs I've mentioned here. Cresselia doesn't need to worry about her Special Defense so much because it's already naturally very high, and Calm Mind boosts it anyway. 252 Sp. Attack EVs, on the other hand, are very important due to Cresselia's naturally low Sp. Attack. By requiring more Calm Minds, a lack of investment will make it much harder for Cresselia to deal decent damage and get past her foes. Investment also makes Cresselia much more capable of fighting back in the event she can't set up any Calm Minds at all. Compared to full defensive investment, Cresselia deals about 33% more damage but takes about 15% more damage from physical hits; It's trade-off which in practice has consistently shown to be worth it.
Outside of the basics, Psychic is your STAB attack. Max Sp. Attack helps Cresselia get past other Pokemon that boost their Sp. Defense, including other Calm Mind users. This means that Psyshock, which hits the opponent's defense, isn't too necessary here, especially since it has a lower Base Power. Just a single use of Calm Mind will let Psychic faint many Pokemon within two hits. Moonlight is important both to help get Calm Mind Boosts and for general tanking ability; With Cresselia's great Defense and Calm-Mind boosted Sp. Defense, she is not going down anytime soon as long as long she can recover half of her HP with Moonlight. As for the final slot, Moonblast is easy to get on Cresselia and is a very solid option overall for Dark Types, but a Fire-Type Hidden Power is highly recommended if you can use it to hit Steel-Types, especially Scizor. Without it, Scizor will see Cresselia as a handy invitation to switch in, use Swords Dance, and try to sweep your team. Hidden Power Fire can OHKO most Scizor after a Calm Mind Boost. Other than that, HP Fire can hit Pokemon such as Bisharp, Ferrothorn, Weavile, and Klefki.