There will be no conveniently placed Super Furnaces or any other external gimmickry to aid Kain. He only has his powers and the Soul Reaver.
Can Kain overcome Dumah at all? Dumah plainly says that Kain is not his equal (being trapped in the spectral realm for centuries and all). Unlike his older 'brother' Turel also claiming to be greater than Kain out of sheer blind arrogance, Dumah actually backs up his claim. Dumah is the most durable being in the soul reaver series. And probably the physically strongest as well.
Dumah laughed off at any offense Raziel could muster. Whether it be glyph magic or even the Soul Reaver's strikes/psychic blasts. (Compare that to Kain simply being hurt by Raziel's claws) Not to mention that like Raziel he existed even in the Spectral Plane, where he was completely invulnerable.
Unlikely. He won't be able to do anything if Kain goes mist and sticks the Reaver through his heart. Or he can use that spell to exsanguinate every drop of blood from Dumah's body.
Dumah may be physically superior, but that's all, Kain has a 1,000 ways to dispatch Dumah easily.
Him shrugging off the Reaver is a gameplay mechanic. He wouldn't be a very threatening boss if you could strike him down in one hit with the reaver now would he? I obviously don't mean he attacks in mist form. Kain could easily go mist and attack from behind, which Kain has been known to do.
You also failed to address my point about Kains magic. Nice try yourself.
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Dumah waz only immune to teh reaverz becuz of game mechanix. Guess what, it didn't one shot other bosses.. The fact is, if Kain or Raziel can't actually peirce their enemy's skin, they can't steal their soul.
IE, if they didn't want the boss battle to be too easy, they could have made Dumah capable of being hurt by the reaver. Instead, they made a point of showimg Dumah as invulnerable.
There was little indication that Dumah's skin was any thicker than normal. When you start the fight Dumah is sitting is his throne impailed through his heart, so his skin is obviously able to be pierced. Even if it wasn't Kain has all of his magic which he can use to dispatch Dumah.
Kain is the most powerful in his Vampire clan and is always given the best part of the Dark Gifts, Dumah isn't winning this.
Raziel's Reaver isn't intagible, it's the Physical blade in energy form. If it was intangible it wouldn't do anything. Dumah was killed by fire, honestly Kain doesn't even need the Reaver in this fight...
So... Kain has been able to produce blasts of fire. No furnace nescessary. You've still yet to share with me how Dumah is going to survive a blood letting...