Bookworm Adventures Deluxe

Put the game in windowed mode and fine an online anagram creator.

Put all 16 letters into the advanced anagram search, and select "show candidate word list only."

At the top of the list is the very longest words possible from the given letters. Have a blast! I've gotten a 14 letter word from this.

When you beat Codex, the word that Lex spells (it is a really long one that is always the same and does not use any words on the tile grid) is (Get ready, folks)
HIPPOPOTOMONSTROSESQUPIEDALIAN!
This word is so powerful it traps Codex in his pen, therefore beating the game, gaining the magic pen as your last treasure and unlocking Arena mode.

In chapter 3-9, (Dracula's Castle) after you beat Dracula, there will be a cloaked figure behind him, which turns out to be - Professor Codex?

This is a tip for beating him:
Use the Aegis of Athena, the Hand of Hercules, and the Endless Gem Pouch. Then spell ~7 letter words and power them up to defeat the summoned bosses. When you battle Codex, spell words that are as long as you can, and don't be afraid to use scramble! Make sure you have around 10 of every potion, and after a while Codex will be finished!

Need a scramble in arena mode, but are just about to start a battle and will lose too much time if you do? This cheat works, and will help you scramble easily. (Note: this only works in arena mode)

When you hear someone say '3...2...1...Go!' you can scramble when it reaches '2', and you will start the next battle with a fresh set of words and an empty timer.