I finally got it...the Wood Magic Swordsman! Q_Q
I have ran about 10 runs of Master and more Expert, and I didn't even see trace of him. Then when I finally did see him, he dropped the egg for me, without the x2 rate Q_Q
It was a pretty rocky run though, first I accidentally killed both grunts on 1st floor due to some insane long combo, and met him on 2nd floor without full HP, so I had to use 1 stone to revive.
After that other than mid-bosses, I barely had 1 turn being full HP, and didn't have time to store skills, so I pretty much blasted most of my way through by combos only.
The Dryads also decided to pull a 22 on me, when I just used Fire Resist's skill on the previous floor because my screen is filled with almost nothing but water orbs...good thing I survived in the end Q_Q
I think I'll stop here and farm for him again in the distant future...still need to prepare my Amaterasu and other Resist Dragons better so I can challenge the Master level of Dark Sky Dragon in the following weeks...