you go to the town above it. sootopolis city. and then you talk to the people in the city . if you talk to everyone and nothing happens, then you have forgotten to do something in an underwater cave. if you talk to every1 and you did something in the underwater cave, then someone will let you into the cave of origins. you will meet Wallace and he will ask you something. you say sky pillar and he will give you the key. p.s. the 1st time you see rayquaza, you can't catch it. the second time, which is after you defeat the elite four, you will have 1 chance to catch it.
There is no key it opens when you become a Pokemon champion.
sky pillar on the sky pillar on rt 114
At Sky Pillar.
you have to go the sky pillar
the route that sky pillar is on is 111 above the town Mavville city. the sky pillar is in the desert hope this helps
the sky pillar is located in near the pacifidlog town, there you can find banete and claydol.
go to the sky pillar
that's in emerald
in the sky pillar
say hi
beat the elite four
go up sky pillar