I've got a few thesis' here when it comes to Ralan Bek. This will take a very, very long time to unravel, so I may put this into multiple posts. If I do not, please, please, please bear with me. It is a lot of rambling and most likely a lot of evidence that really has nothing to do with the topic at hand, but somehow, in this warped little mind of mine, deemed relevant. And thus, with that apology out of the way, comes the main point, being that I have a slightly different thesis as to the nature of Ralan Bek. So, without further ado, here you go:
1) As to which shard of which god he has in him, it could go either way. I would be more inclined to say that it will be the a sort of hybrid (as some of you suggested earlier, though my idea my be a bit different), though, for a few reasons.
A) For evidence as to him being a shard of Nalar, there is the scene in the basement (?) of the secret Nighthawks base, when the priest (or whatever he is) approaches Ralan and says that he recognizes "something familiar....his master" in Ralan.
B) However, we are told that the Dasati Dark God is in fact more powerful than Nalar. This is critical to the argument (sort of, I just wanted to say that sometime).
C) I would argue that there is the possibility that the priest was confused as to which presence he felt in Ralan. After all, both Nalar and the Dasati Dark God are of similar natures; both "evil," though that term is used lightly throughout the books, both mad (or semi-mad, it would seem, in the Dasati Dark God's case).
2) Of course, a problem that comes with these facts is one easily overlooked: that the Dark God of the Dasati is in fact a living, physical being, albeit an incredibly powerful, dark, and most likely as close to immortal as can be (or truly immortal in fact), kind of being.
So, in this case, I would find it hard to believe that Ralan could possess a shard of the Dark God in him; I don't think such a god, especially after the mess with the true Talnoy (a.k.a. the Lost Gods of the Dasati, the ones Macros secreted away in the cave on Novindus, not the fake ones Macros indicated were placed on the battlefield...who, from what I remember {although I could be wrong} were created through a proccess, ironically, closely related to the Black Slayers of Murmandamas.....coincidence?).
3) Still, I am disinclined to believe that, as I believe it was Macros who said, that since the Dark God of the Dasati is apparently a physical, living being, that he is indeed truly more powerful than Nalar.
4) Also, I would point to the small insights as to the nature of Nalar, the universe, the nature of the Midkemian gods, and apparently life in general, that are revealed in Rage of a Demon King by Nakor. These also parallel with strange little tidbits of information we are given, at random points, throughout almost every book, coming mostly from Macros, but also at times from Pug and Tomas.
A) I think, as revealed throughout the many books, though most notably in Exile's Return, Rage of a Demon King, Shards of a Broken Crown, Flight of the Nighthawks, and Into a Dark Realm, that the role of the Valheru, and how they actually affected and caused the Chaos Wars (and the Chaos Wars' apparently many manifestations throughout the cosmos), will play a much greater role in the books to come, and ultimately the fate of the universe itself. I believe there was also something in Krondor: Betrayal, but as I do not own the book, and it is currently 12:21 in the morning, I am slightly disinclined to look for the passage I mentioned. However, I do remember it was in one of the parts where Pug is looking for Gamina.
B) As Rage of a Demon King (I think) revealed, via Nakor, the rebellion of the Valheru in essence created the Chaos Wars, after they had already started. Indulge me in this, please. Nakor talks about the nature of the universe, and aided by Dominic (who is also a major contributor of this knowledge), and how the "Chaos Wars," as they are classified, were really the expelling of energy from the multitudes of cosmos' and the layers of reality. I classify the Chaos Wars differently only because in my mind, they really started when the Valheru first began raiding across the cosmos, which began the proccess of the many layers of reality, planets, and in a sense "layers" of the cosmos beginning to try and right themselves.
C) Oh, and while I cannot come up with any good reason as to why I am putting this in here, do keep in mind the fact that the Dasati world is parallel to Midkemia, and that the Valheru did raid even there. *See side note* And keep in mind, though I don't enitrely remember what the stated reason was, was it not through some action of the Valheru that the Dark God was able to take over, and cause the veritable "destruction" of Dasati society?
*Side note: it is therefore surmisable, and probably talked about, that the Valheru most likely raided a majority of the different levels of reality and "layers" of the cosmos, which would explain the Chaos Wars. Also, if the Midkemian Gods are the result of the expelled energy of all the "layers" and different realities of the cosmos, or really the universe, attempting to undo the problems caused by the Valheru, it would seem logical that the Midkemian gods are in fact more powerful than any other gods, including those of the Dasati. And, it would thus conclude the fact that, as we are told multiple times that the basic stuggle all the characters undergo, and the threats faced by the characters, are "repeated" throughout all the "layers" of the cosmos and different realms of reality, the Midkemian Gods are in fact the "physical" manifestations of all the other gods in the cosmos.*
5) The last bit of evidence I could really think of was the details we learn over the many series of books about the truly vast scope of Nalar's powers. We are told ( in which book I can't for the life of me remember) that it was Nalar who influenced Draken-Korin to create the lifestone, and thus influencing the rest of the Valheru, save Ashen-Shugar *See Side Note 2*, to rise up against the gods. It was Nalar who also, in turn, influenced the Lesser Gods to rise up against the Greater Gods ( I know that detail is in there somewhere, probably in Into a Dark Realm, but I am not going to bother putting a page reference, or taking another half hour to come up with evidence backing up that statement).
Would it not be too much of a strech in logic to assume that perhaps Nalar influenced the Dark God of the Dasati, as well?
Although I don't where it ties in, I would assume that the remaining gods were not influenced by Nalar in their decision to cast out the Valheru from the universe, or at least from their "layer," as they were also obviously not influenced by Nalar to cast himself out. Whether or not it was Nalar's influence that caused the Valheru to raid across the cosmos is arguable, although it seems it is in their very nature. Although I think we can all assume Nalar appreciates having the Valheru as his sort of "tools" to use as he wills. *See Side Note 3*
*Side Note 2: This parallel between Macros, Tomas and Ashen-Shugar has got to make you wonder, when it comes to Macros' (and later Pug's, though that is not relevant right now) time-traveling abilities, is this simply a gift from Sarig? Or is it a result of everything really being under one, simple, ordered "timeline," so to speak, until he gains this ability, thus throwing the entire cosmos as we know it into disaray, and basically creating the entire storyline of all of Midkemian history as we know it? This brings up another question: what exactly was Macros' reality like before he got his time-traveling ability? Perhaps I am just rambling, but it is an interesting question.*
*Side Note 3: This note is not actually tied in to the ending of point 5, as it seems to be, but rather a continuation. Basically, as I see it, all of this smacks of the reasoning that the Midkemian reality is in fact the "true" reality, and somehow, every other "layer" of either the cosmos or reality itself is somehow simply a reflection of the Midkemian cosmos.*
OK, ENOUGH OF MY RAMBLING!! BACK TO THE MATTER AT HAND!!
6) Remember how there were apparently 3, although it might just be 2, different ways a god could impart themselves on the world? A) As an "echo" of sorts, which I still do not understand very well, B) as a shard, or fragment, which makes a lot more sense than an echo, and C) as a dream, or a memory. *This is NOT including the avatar method used by Sarig* Well, because like that priest felt, there seems to be the presence of Nalar in Ralan. I would argue that the Dark God of the Dasati is in fact a sort of avatar, or better yet, an echo, of Nalar himself; that this would explain why not only the priest but also Nakor recognized the presence of Nalar being in Ralan, but why Ralan seems more at peace in the Dasati realm...he belongs there.
Whether this is because he is in fact the God Killer, a rather distinct possibility, or simply because the ordered violence and brutality appeal to a nature such as his, is up for debate.
If because of the first, it is perhaps possible that he is in fact fated to replace the Dark God of the Dasati. Another possibility is that upon killing the Dark God, he has fufilled the will of Nalar, and would thus be "reunited" with Nalar.
At this point, I also don't think Nakor's "removal" or "tempering" of the shard is really relevant at all.
7) TO BASICALLY SUM UP MY POINT, I think that Ralan Bek is in fact either an avatar, or maybe just a shard, of Nalar. But I think that as a shard, or avatar, or Nalar, he is influenced somewhat by the Dark God of the Dasati; and as I see the Dark God to be simply a physical extension or avatar of Nalar, simply in the Dasati realm, it would make sense that when Ralan enters the Dasati realm, he feels at peace, because he is in harmony with one or more of Nalar's identities.