Doppleganger

There are 2 of them. 1 in the underground caverns (inverted water vein) and 1 in the outer wall. He can be pretty annoying since he jumps around all the time. Try to see a pattern in his moves so you can hit him better. Be sure that you use the shield; it is a must to block the knives and other sub-weapons. However, he can still hurt you by hitting you with his sword while you have your shield deploid! The problem with him is that if you cast a spell, he'll turn into fog and it won't work...to really kick the crap out of the first one, get the Jewel Knuckles (See Tips on how to get them early). Not being able to cast spells on a boss at this points severely limits your ability to him. The problem that'll arise with using the Knuckles is that you lose range for power. Since he has a sword, you'll have to time your strikes (example: when he's jumping). The second fight is more of the same, but you'll be stronger now.