Can anyone give me a clue about how to beat the boss?

I really don't know what I'm doing wrong. No matter how many times I've rearranged stats/equipment and whatnot, I'm still getting massacred everytime I try that battle.

I've actually gotten past the first part once or twice, but even when I did I could never knock down the next one's health to more than 85%.

It's just so disheartening.

Did you read the status the boss has in the first part? It's an important clue to what you'll need to do in order to be able to defeat her next form.

Do let me know if you still have trouble, though.

I've read it yeah, but what I've gotta do isn't coming to me.
I'm thinking I'm not supposed to use my proficiency abilities.

My non-tank pets are going down so fast though that they're pretty much dead before I even get to the 2nd form.

Okay, totally figured it out.

Thanks for the help Draco.

Wow, I just attempted the dungeon for the first time today and never even made it to the boss. The dark elves totally obliterated me into mewling paste. Time to spend some cash and gear up, I think!

***SPOILER***

Yes, the boss on this is a killer. For the first part you have to be super careful, because every enemy killed powers her up, at least that is how I understand it (meaning using attacks that hit multiple targets are a really bad idea here). And during the second part one of her attacks steals your pets mana and heals her with it. By use of tons of potions I managed to get her down to 45% before I got completely wiped out (most of that using hp potions as much as I could so that she couldn't steal much mp when she did take it, which kills my regular style of attacking). At that point I had already been attacking her for 10+ minutes or something and was utterly sick and annoyed of trying to deal with her, not having revive potions that would help my pets revive in any shape to stand for more than 1 or two rounds, and potion cool down.
As far as the story line goes, not a bad game (but hey I like stories so it doesn't say much). But comparing to a MMORPG I love to play the fighting style is only so so, and making what I would consider a decent tank isn't possible. (These are more of a meat shield than a tank). The pets stats get stretched way too thin so that by putting something in health or defense it takes away from damage, put something in damage it takes away from health and defense. It is like all of them are playing tug of war against each other rather than complementing each other. And it seems even with good agility pets rarely ever dodge any attacks. I guess I still have a few things to learn about how to set up pets right in this game.

That's pretty much it. Don't let your mana build up unless you're going to use mend and even then only let it build up to about 30.

**SPOILERS** Maybe, LOL

If I'm not mistaken, the shade uses leech mana and heal for every 5 turns, you will need to get used to this pattern. I build up my mana until the third turn, used my finishing blow on the fourth, and on the fifth turn because my pet is slower than the shade when he used the leech mana my pets had 0 mana, but I still command them to attack on that turn.

The trick is getting to use finishing blow before the turn he uses leech and heal, if your pets are slower than him. DX
It was a pain at first, but I got used to it after a few times.

Does anybody know what stat is needed, at what amount, to open the first door you come across, that you can use your syslesti to open?

The lowest stat I've used to open the door was around 700... if I remember correctly that is.

I usually use my mission pets to open them. So, whenever I encounter that door, I went to my party page and change one of my party Sylesti into the mission ones then explore the area once again.