: [...Alric] has ressurected the Watcher, and even worse
: Rabican [...]. He also has made b'yaggo comporeal.
: Fearing his powers may not be enough Alric calls upon
: the spirits of dead arch-mages who's souls he cannot
: ressurect, Soulblighter is among them, he uses their
: spirits to expedentially increase his power.
The only major flaws I can see are all the mentions of bringing back ancient and tireless evils. Firstly, besides gods, there is no proof that a being can be brought back from the dead in Myth. But some way or another will be imagined up for that to be possible, so I'll move on to the choices of people being resurrected.
Alric invested many of his loyal men's lives, much very precious time, and risked his own life setting the trap that killed the Watcher in TFL, which we all saw with our own eyes (hopefully, I don't know if everyone played the game through but I certainly hope we all have). The idea of Alric actually bringing this man -- one of the most ancient terrors of all things good in their world -- back to life is perfectly risible. I can hear it already: "But Welly, desperate situations call for desperate actions". This doesn't apply. Why not? Someone as powerful as the Watcher himself cannot be bound by anything less than a god [Balor]; otherwise Myrdred would have done that decades ago. Therefore, if he comes back to life, he cannot be trusted nor bound. Besides, logically thinking, he would never willingly ally himself with the man who killed him. Instead he'd join the winning side. So bringing him back would therefore be less than ideal. It would create far more problems than solutions. If the Watcher can kill Mazzarin, he can find a way to screw Alric big time if he's brought back, and then collect his reward from Alric's enemies.
Next: If it was possible to make b’Y’laggo corporeal, why would Alric ever do it? Firstly, it's the diety that is worshipped by his allies' [fir'Bolgs] worst enemies. Bringing b’Y’laggo into the picture will surely please the Bre's, but will certainly not make any fir'Bolgs happy. And the bre's have attacked your men before and jeopardized the mission to bring in Myrdred. Alric has no business ever allying himself with the blood enemies of his friends. Besides, bringing in a profane elemental spirit into the fold even sounds bad. The implications and huge question marks would be as bad, or possibly worse, than bringing in the Watcher.
Someone will likely say something like: 'well, the bolgs and the bre's will just have to be allies for the time being'. That quite possibly would be the biggest crock of a defense argument that could ever be proposed. Why? In Myth II it is clearly stated that these two races are unquestionably blood enemies: "the fir’Bolg have been honing their martial skills on [the bre'Unor] since time before memory". Even in the face of mutual destruction they will doubtlessly be trying to screw one another over. It's like Ghols and Dwarves hanging out together sharing a beer: utterly impossible. It's not ever going to happen. A hatred of that level cannot be merely forgotten about all of a sudden. Not when you've been terrorized for countless generations by one another.
Moving next to Soulblighter. Let's see: the latter individual spent much of his time and resources trying to kill Alric in TFL. And possibly even before that. What happens 60 years later? Soulblighter again throws his all at Alric in an attempt to obliterate him. But what does Alric do? he winds up killing him for his troubles. And saves the known world in the process.
Resurrecting those people would be like trying to put out a fire with a bucket full of gasoline and a loofah soaked with petroleum. Tapping the resources of the Dark to fight the same Darkness is no different.
My bottom line is: if you're dying from dehydration, you only drink the sea water if you just want die faster.
-Welly