Where do I get Regirock, Registeel, and Regice. I never played Ruby or..

Well, there are three different routes you can catch them on, and all include tasks to accomplish. The tasks are in braille, so I'll tell you what to do. You need a Pokemon with rock smash and one with flash to cach the regi's.

Once you enter a cave, go to the back of the room, and there will be a carving of braille letters/ words. Press "A" on it.

Regirock- Southern Desert. Go left, left, down, down, and then use rock smash.

Registeel- Route 120/121 (I forgot). Go to the center of the room and use flash.

Regice- Route 105. Walk around the room once, touching the wall and not crashing.

To unlock all the doors to their "lairs", you have to do a mission first. To do these missions, you need a Pokemon with surf and dive, a Pokemon with dig, and a relicanth and a wailord. Go to Pacifidlog, surf to the left. You have to venture through the fast currents, and there are multiple ways to accomplish it, so I won't say a word.

You have to figure it out on your own. Anyway, you'll come across a place where you can dive. So, dive. Go to the bottom and there you will see a place where there is a carving with braille letters.

Go in front of it, press "A", and dive to the surface. Go to the top of the room, and you'll see a carving with braille letters. I think you have to use dig. If you do, the door might open. Go inside and to the top of that room, and it will say a long message. I think Relicanth has to be first in your party, and Wailord has to be last.

Once, you're done "reading" the message the screen will shake, and there will be the sounds of doors opening in the background. If this doesn't happen, then Wailord has to be first in your party while Relicanth is last. The doors are the doors to the caves where all three regi's are.

I'm sorry if this is a little confusing, maybe someone else will say how do catch them in a better way. Please rate this answer, so I can know how confusing this answer is.