I can't seem to get a valid inspiration for how to convert the Tooth to a 4E artifact.
I know exactly what you mean - I was struggling myself a month or two back. I think a lot of the problem stems from the fact that the artifact is just so BORING, even if you read Tome of Magic (pages 78-79), or even if you try to look back at say 1st edition - in fact, all the Teeth of Daillver-Nar are quite boring, and there's not even a big "item set" kind of effect. In my opinion, to call them an artifact is kind of stretching it, and if you do, you run the risk of inflating the player's expectations, or you'll need to boost it substantially to make it a worthy 4e artifact...
Personally, I decided to try and make it a worthy 4e artifact, but keep it a little more "in the background" than typical, as it's going to hang around from around 12th level to early on in the Epic tier. Here's what I came up with:
it occupies the head slot,
gives a +2 item bonus to grab,
gives the following monk powers (as a monk's implement +3):
Strike the Avalanche (when Satisfied, but owner takes -1 to all d20 rolls if they have not stolen a precious item in the last 24 hours),
Diamond Mind (when Pleased, but take -2 to all d20 rolls if have not stolen a precious item in last 24 hours).
I haven't really worked out the artifact's motivation(s) yet, beyond stealing stuff, but plan to look at Malcanthet's motivations in future adventures i.e. the tooth/teeth should be larger part of making her will happen. So one of my group's PC's, a bugbear rogue, is "wearing" it, and feels the compulsion to covet stuff that's not his, and gets a free Monk power that's marginally useful (although he's never used it yet), and as the adventures progress I expect I'll get around to working out more motivation, and if he steals more stuff, levels up, etc, he'll get to the next level (Satisfied), and so on.
The Tooth of Shami-Arnourae comes up later on too, like around Epic tier in my game plan - its power is even lamer than the first, but I planned to have it include some kind of Psion powers.
Actually, reading Wells of Darkness gives a lot more info about Ahazu the Seizer, and page 82 gives more powers that could be given to the Tooth. I'm not so sure my monk-based powers are the best now... Something like this might be OK:
Gain blindsight 1 square per level (max 20).
Shunt a creature within 30 feet of you into the void between the planes ; creature can’t act until the end of your next turn (Cha vs Will, daily; there's a wizard or warlock power like this somewhere).
Touch as per Unholy Blight or 4e equivalent (encounter).
Void Mind immune to mind-affecting and soul spells (at-will, probably like the monk utility above).
Revised as follows:
Occupies head slot.
Gives a +2 item bonus to Grab attempts.
Grants Blindsight out to 1 square per 2 character levels (max squares = concordance score).
Adds the following powers:
Crack the Skull (barbarian 13, encounter),
Diamond Mind (monk utility 16, encounter; when satisfied),
Wrath of Acamar (warlock 19, daily, functions as implement +4; when pleased).
Goals: covet and steal precious items; imprison your enemies alive in a dark hell hole, rather than kill them or let them escape.
The concordance score rules need some work, but given the artifact is expected to be around a lot longer than usual, I expect one needs to flex these somewhat (adding less per level, or adding plenty of penalties due to non-compliance, otherwise you'll hit and exceed the max score pretty quickly).