[NicknamedBob]

"... they use a phrase Eotain Shrdlu. Supposed to mean something like 'Sieze them' or something."

Darks, I'm surprised at you.

Anyone who has ever tried to puzzle out a coded message should recognise the first twelve letters, as most commonly used, in the English language.

Etaoin Shrdlu.

If a phrase is encoded by letter substitution, find the most commonly used letter in the encoded text, and substitute E. Then continue to the next most commonly used letter. Any three-letter combination is likely "and" or "the", so try those combinations.

Keep working at the puzzle to discover more letters until you work out the phrase.

PIX QI ORSA ALIR CSY LEZI JMKYVIH SYX XLI ERWAIV.

[Baraonda]

You need a computer to figure out that riddle. I think I = E.

[Darksheare]

In the web comic Girl Genius, they use it as a statement to mean "Sieze" somebody.
Center panel, here:
http://www.girlgeniusonline.com/cgi-bin/ggmain.cgi