You have to bring an arceus to the shack in the middle.
you go somewhere
I beat the whole ruins of Alph "mystery" and I didn't discover a secret.
learn surf
There are two "caves" in the Ruins of Alph. The first is the Union Cave, which leads into the Ruins of Alph. The second is a series of caves which lead to the unown.
Nothing in the ruins of alph reaches arceus.
On the patch of grass on the west side of the Ruins of Alph
Steven will never appear in the Ruins of Alph.
Go through the union cave and find the secret ruins of alph entrances that u have to use surf to get to. Use surf near the entrance to union cave you should find it quick. You will find two passages that lead to two different jigsaw puzzles in the ruins of alph. One of the passages leads to a place in the ruins of alph with grass search there and u will find natu and smeargle.
in Pokemon heartgold ruins of alph in Pokemon soulsilver ruins of alph
go into the smaller ruins and slove the puzzels on the wall. The floor will open and you will fall into the ruins of alph. You will then find unown in the ruins.
go to the union cave. go up as far as you can (you need HM surf and HM strengt). then go left. there are two exits there. they both go to the left part of the ruins of alph
It isn't at the ruins of alph. It's in between the Kanto and Johto region.