Currently accomplishing something I never did in any of the Pokemon Mystery Dungeon games: recruit all the legendaries. I've intentionally put off recruiting Dialga, Shaymin, and Regigigas in Sky to focus on the others. Missing only 2 of the Unown and I've recruited all of the legendaries that appear via the Secret Slab/Mystery Part save for Celebi, which is one of the legendaries/mythicals I'm saving for last. Have yet to recruit Rotom as well. In a past playthrough I've done all of the seven treasures and recruited their guardian legendaries, but in this current playthrough the only one left is Giratina, who I seek to have as the last legendary I'll recruit. Still waiting for the challenge letters from Entei, Raikou, and Jirachi to show up. Also haven't gotten the Labyrinth Cave quest yet, which I seek just to unlock all the dungeons. Could use a Wonder Mail generator for all those, but I'd rather wait for them to appear naturally in the game as it seems only right.
Now each of the legendaries have their own exclusive items, which are only found at five locations depending on the legendary: Croagunk's Shop, Miracle Sea, Spacial Rift, Concealed Ruins, and the Zero Isle dungeons. The latter four locations all require a Key in order to get one of those items, and even then you may not get the one you want as it's all randomized, so saving before tackling the place is key. No need to worry about Zero Isle Center as there's no exclusive items in it save for the team leader if you make it to the end. Could use a Wonder Mail generator to help me with those items, but I'd rather do it the way the game is meant to be played. Far easier said than done as the Zero Isle dungeons are anything but easy, so I'd be better off trying to max out the stats of the Pokemon I want to use for those, including IQ skills. Also don't seek to level up a legendary until I know I have access to their exclusive item. For example, you can potentially get Cresselia's exclusive item before you go to Dark Crater as her exclusive item is located in Spacial Rift (incidentally, so is Rotom's). As for her counterpart, Darkrai's is in Zero Isle North, which is also the only one of the Zero Isle dungeons I've ever tried in any playthrough. I know for certain I can get the exclusive items of North as while I never completed North, I went far past the floors that had the exclusive items. As for getting keys, you can either buy them at the shop for a hefty fee of 8,000, or get them for free as they're randomly spawned at Aegis Cave (considering all the restrictions Zero Isle has, I think they may be spawned randomly there too).