Instructions
Travel to the Ruins of Alph in "Pokemon SoulSilver."
Solve the puzzle in each of the four chambers. To solve the puzzle in the upper right chamber, use an "Escape Rope" item in the room. To solve the puzzle in the lower right chamber, use the battle move "Flash." Place Ho-oh at the first slot of your party to solve the puzzle in the upper left chamber. Solving the lower left chamber requires you to have a "Water Stone" item in your bag.
Capture the first 26 forms of Unown by traveling throughout the chamber and using Pokeballs to catch them. Once you have captured all 26 Unown, travel to the main entrance of the ruins. Another area will open up.
Go into the new area. This area contains the final two forms of Unown. Capture them using Pokeballs.