ejiki: And Yes! I solved it. The game is Crusader Kings II ! Thank you for the game, and even more - for the puzzle!!!
But... You know what... I didn't solve fourth hint... I still don't get it... it's definitely Vigenère cipher, but then the key can't have numbers... then pieces of letters with digits on line ends - isn't the key? Where is the key then? Can you tell, what was correct solution step-by-step?
blakstar: If you worked out that the game was Crusader Kings II, that was all you needed to decipher the key -- as for the letters and numbers at some of the line ends that was just me trying to throw a spanner in the works! It basically read "FAKE KEY"
1. What word do these have in common: Air, Elephant, Water.
GUN 2. Wrathful thirteenth-century Latin hymn, minus the last letter.
DIESIRA 3. Fourth letter of the surname of a British naval officer who died at the Battle of Trafalgar. NEL
SON
4. (Sorry! This clue's been encoded! The key is hidden somewhere in this post) 2003 twyli osgqh ku Zvvlv'l vxwgo Jbnwohxgg.
The key was "hidden somewhere in this post". Deciphering the clue gave "2003 movie based on Verdi's opera Rigoletto" RICK So you should have got
GUNDIESIRASRICK, which unscrambled is
CRUSADERKINGSII.
Apply that to the encoded Steam key, and you've got the original key back!
Congratulations anyway -- no matter how you solved it! :-)
Bleh. I got as far as "GUNDIESIRASRICK" but couldn't make out the game name. Congratulations to the winner and thanks for the enjoyable challenge.
I especially liked the key for the cipher in number 4.