hey guys .... i need help for those who have got mylen Artifact ... i know it drop from those two guys in the hidden room with no respawn ... how in the world did u guys get it .... and plz dont say luck cuz i will killl someone ..... thnx

This was a bit tricky because of the no respawn but some of the others were the same, like Roka's with the Bahamut from memory.

In most cases, I ignored the artifact's on the first run.
I concentrated on clearing the victory conditions first, if I was lucky I got the artifacts.
Then I redid the dungeon concentrating on the Bonus conditions and artifact gathering.

You can try save scumming.
1). Save the game before the kill.
2). Kill the monster. (with both Ful's Mil and Ful's Tears if possible)
3). If no artifact drop, reload game, skip to next turn, go to step 1.

Don't remember Mylen's specifically but if you keep trying you will get it eventually.
It really does just come down to the unmentionable L word.