Does anyone know how to get to the second floor of the Abyssal Ruins? I tried simply "talking" to it, but it did not open. I do have two Pokémon with me that have Flash and Strength.

East of Undella Town there is a dark circlwe in the water. Use Dive with a pokemon on it to go under that water. Do you need to know how this place works? And you dont need Flash (I dont recall).

Oh, I was able to get in, but I couldn't get to the second floor.

Ooh, i figured it out. I think you have to get to the pillar before the second noise from the torrent.

Edit: Actually, it's even less than that.

Also, I'm curious, does anyone know how to decypher the jumbled messes after the first floor? The first has a bunch of reverse text (including an MLK reference, MAERDASAHGNIK). The upper floors must have some kind of basic cypher applied to them.

Edit 2: It's a Caesar Cypher with n = 3, otherwise known as ROT-3, then written backwards like the others! And yes, I was bored enough to solve it on my own.

Though you already figured it out:
To 2nd Floor: Get there without backtracking. "No King gets lost"
To 3rd Floor: Use Flash on the pillar.
To 4th Floor: Use Strength on the pillar.
I went there just yesterday because I needed some quick cash, and it was a mystery. I managed to get all of the items on the first 2 floors without using a map. I had to by the time I got to the 3rd, though, because I got really nervous. Oh come on, the constant "The sound is close!" HAS to frighten you somewhat. And like Cat I also translated all of them. Every time it goes up a floor, the words remain backwards, but all the letters shift down one. I don't know about the circles, maybe they're numbers?

Of the few messages I looked at, they almost seemed religious, but it could be because the concept of separation of Church and State didn't arise until only a few hundred years ago.

They're encrypted via Caesar Cypher. I'm thinking of going through and decrypting all of them.

This comes from my notebook from months ago. I think I copied it off a site, but I don't remember which one.

1st Floor

Listen to King's words.
Primes lead to truth.
King is kind.
King never loses hope.
King is brave.
King has a dream.
King is adventurous.
King accepts all.
King turns 2nd corner.
King turns 3rd corner.
King turns 5th corner.
King turns 7th corner.
Here we praise King.
Have the heart of King.
King's light shines.
King moves his people.
King acts with love.
King fought hatred.
No king gets lost.

2nd Floor

Life is gratitude.
Good or evil isn't all.
Eating is receiving life.
One must not waste.
Do not be barbaric.
All is precious.
Wars create tears.
Shine if agreed.

3rd Floor
King talks to all beings.
Saved all from waves.
King is hope for all.
Think act with love.
Act strong if agreed.

4th Floor (I have a note saying missing words or numbers)
King defeated __ alone.
__ joined King in a day.
King called __ beings.
King is hope and future.
The great King __.

I oddly remember a bunch of funny symbols.

If I be honest, I have never even ventured into the ruins yet. I got all the plates anyway from my old Black version.

Wait, how did you do that? Items cannot be transferred from Gen IV to Gen V.

Oops! I meant Black! I did the ruins on my old Black version (used a guide) but didn't bother on Black 2. Sorry for the confusion!

This is a little off-topic from the rest of this thread, but has anyone else noticed that if you exit the ruins manually without getting flushed out you can reset the step counter without having to use Dive again?

Saved me a bit of time and sanity on the first floor.