Aside from Dialgia, Palkia, Cresselia, Manaphy, Groudon, and Shaymin becuase I already have those.
P.S. I know you can get many other legendaries becuase I read it on the internet
scizors special missions give articunto, groudon, mew, girantina, heatran, rayquaza, and kyogre.
jirachi can be obtained in star cave (spindas juice unlocks wish cave)
darkrai by putting a mystery part in your bag going to miracle sea 3f and he will be sleeping as you spawn
zapdos must have secret slab or mystery part in bag amp plains 7f
moltres giant volcano 10f must have secret slab or mystery part in bag
mewtwo sky stairs 49f
legendary dogs challenge you at ranks Suicune at master raikou at master and entei master
regi's must return to dungeon after traveling with team charm
lugia surrounded sea 18f mystery part needed
ho-oh mt. mistrail 19f mystery part needed
celebi mystifying forest 10f mystery part needed
latios10f and latios5f (deeper) are in spacial rift mystery part needed
deoxys shimmer hill 17f mystery part needed
lake trio return to their homes
shaymin return to the peak
dialga return to temporal tower
palkia spacial rift
dang that is alot!
(note: arceus is unrecruitable)
Go to serebii.net and look for the tab explorers of sky (or time/drkness) itll give you the wonder mail things to type in and get the dungeons with those pokes in it!