Uhhh... numbers...

Yep, that was my initial reaction to this puzzle as well. The idea is to follow the clues of the Lords in the correct order. For all those interested, here's the exact calculation you're supposed to do.

First, Lord Might mentioned that you should start with his number, and that it's "two primes less than twice the crystals in this mess". If you counted them correctly, you'd find there are 13 crystals in Arachnoid Cavern. Times two, that's 26. Now you need to take two primes less than this number. (In case you didn't know, a prime is a number that can only be divided by 1 and by itself.) The first prime less than 26 is 23, the second is 19. So Lord Might's number is 19.

Another thing Lord Might says is that you should follow the other clues "in an order Lord Word would find agreeable". It sounds complicated, but it turns out that's nothing but a difficult way of saying "in alphabetical order". So follow the clues of the Lords in this order: Might(only because he said you should start with him), Accuracy, Endurance, Luck, Magic, Prayer, Speed and Word.

You already have Might's number, so proceed with Lord Accuracy. His clue is "add half the number there could be of you". The maximum number of party members is 8 (six regular characters and two hirelings), so you need to add 4 to the 19 you already had. That makes 23.

Next is Lord Endurance, who said: "Count these thrones, and add that too." There is a total number of 10 thrones in Arachnoid Cavern, so add that to 23 to make 33.

Next: Lord Luck. His clue was: "Add Lord Might's number, then multiply by two." So add 19 to 33, making 52, and multiply that by 2 to get 104.

Now for Lord Magic. He said: "Substract the gongs, then multiply by fifty-two." The number of gongs in Arachnoid Cavern is four, so substract 4 to get 100, and multiply that by 52 to get 5200.

Lord Prayer's next. His clue: "Multiply by the number of gongs to make your answer true." Like I said, there are four gongs, so multiply by 4 and you'll get 20800.

Lord Speed's up next. "Subtract 449 is all you must do." Do so, and you'll get 20351.

And finally, Lord Word, who spoke: "Substract my price, and you will be through." His price for teaching you the Linguist skill is 50 Gems, so substract 50, and you'll find that the final answer is 20301.

Phew, that was a hard one, wasn't it? The reward is worth it, though!