How to catch the regis in pokemon ruby
To catch the Regi-Ice Pokemon, head to Dewford Town and surf north. Find the guy on an island with trees all around him. Head left and up 'til you find an island with a mountain. Head into the mountain, find the Braille wall and press A in the middle of the wall. After a few minutes a door to the Regi-Ice Pokemon will open and you can go catch it.
If you get to regi steel(I forgot where he is) use flash in the cave to get the rest go to ign