About the Hoenn weather titans, the place where you find them is west of Cianwood called the Hidden Tower. That same myth-hunting hiker would be outside the cliff's cave entrance, and this is what he has to say about this mysterious place:
"It is said that on the other side of this cave lies a giant tower that leads all the way to the sky. It is a slightly oddly shaped tower. Part of it is made of the inside of this cliff it seems, and not only does it extends to the sky but there is also a long part of it underground! Moreover, it is said to connect into the sea as well! In other words, this ruins link the sky, land and the sea! It is almost collapsed now however, and only this cave entrance and the tower's central part where a strange pattern is drawn remain.
I believe that there must be an important item that summons the Pokemon who are deeply connected to the land and the sea."
So where do you find these items?
After you have received the Kanto starter from Prof. Oak, go visit Mr. Pokemon. He will give you the Red or Blue Orb depending on your version. He says he received it from a friend hailing from Hoenn, and that it is believed to be an important item relating to the ancient ruins known as the Hidden Tower west of Cianwood, where ordinary trainers cannot reach. But you, as champion of both Kanto and Johto, certainly is able to.
Now you can go into the Hidden Tower's central platform to capture either Groudon or Kyogre, and afterwards, the hiker will approach you again and exclaim that what you just captured was Groudon (Kyogre) which was depicted in the creation myth in Hoenn. In fact, he says the Hidden Tower was built by the people of Hoenn.
Before he leaves, he hints that Groudon (Kyogre) was not alone in Hoenn's creation myth, and he strongly believes that there are still mysteries unsolved in the Hidden Tower. He advices you to consult a genius Pokemon professor, and so that's where we'll go.
At Oak's, he will tell you about Groudon and Kyogre's story in Hoenn, how they fought to shape the land and sea, and the fact that the two were equally regarded. He will not say more until you also bring him the other counterpart, but he hints that according to Mr. Pokemon, the other coloured orb can only summon the other titan by a trainer who has a gold-glittering heart (or silver-glowing soul), which means you need the other game to get the other titan.
When you have traded in the other titan to your game, see Oak again with both of them. He will continue Hoenn's creation myth, adding in Rayquaza's role in pacifying the two. Oak then hands you the Light-green Orb (もえぎいろのたま), which he believes shall summon Rayquaza at the Hidden Tower. Bring the orb to the Hidden Tower again, and you catch your third Hoenn weather titan.
Oh, and if you take the movie Shaymin (or Shaymin caught in Platinum) to the flower shop in Goldenrod, you get the Gracidea Flower.
Steven Stone is also staring at some stones 'he never knew of' at the Pewter Museum. Wonder what he's up to.
That probably concludes my contribution to HGSS for now. Have fun playing, guys!
Coronis~