I have completed the game and I have 4 legendaries to catch.
These were Cresselia and the 3 deer trio, which are Terrakion, Cobalion, and Virizion.
I have 3 Pokemon with max EV and I caught Terrakion on a Tuesday. A day later when I went back to the portal to them, which was when Cobalion was meant to be there, nothing happened.
I waited a day later and still, nothing happened. It just keeps saying that "a mysterious ring is floating in the air."
Please help, because I really want to catch Cobalion and Virizion and it isn't working!
Best Answer
As per my answer here: What are the prerequisites to encounter the legendaries in ORAS?
If you've met all the prerequisites, then you should first confirm the date/time on your 3DS. Ensure that it is set to the correct day for them to spawn. If you change the date/time on the 3DS, all time based events (including legendary spawns) will be disabled for 24-48 hours.
If your 3DS is correct and there have been no time/day based changes in the past 24-48 hours, then the only other cause for them not appearing is that you've previously fought them. You will need to re-defeat the Elite Four in order to have them spawn again.