When do you get Rayquaza in Pokemon emerald?

You get RAYQUAZA at the top of SKY PILLAR after seeing GROUDON, KYORGE and RAYQUAZA in SOOTOPILIS CITY. RAYQUAZA is LV.70 so be prepared! RAYQUAZA knows these techniques:

EXTREMESPEED

REST

FLY

DRAGON CLAW.

The ratio of it being shiny is 25%. The only difference between SHINY & NON-SHINY is that the SHINY one is BLACK, not the regular GREEN. The best ball to use on RAYQUAZA is either an ULTRA-BALL (Or if you are lazy and not bothered a MASTER-BALL!)