Corilithon

Tournaments at my card shop usually top out at 5 rounds! You lucky dog, getting 8.
Anyhow. I've seen versions of this deck before run Coat of Arms (For obvious reasons. Muahaha.) and it works scary well. I think I also saw a version with Pandemonium... somewhere...
Wait, I might have made that last part up. D=

The 19 land concerns me. D=
For a control deck that wayyy, waaaaay too low a number of lands. Think more along the lines of 24 land. I know you have Spectral Searchlight in there but still, that's 23 total sources of mana and your mana curve pretty much starts at 3-4, topping out at 7. Also, signets may help you.

Some rares, such as the Godless Shrine and Angel of Despair (Maybe even Batman a.k.a Skeletal) are much, much better in multiples. If these are only the cards you have, aim for the angels andm aybe a few more of the legendaries, for the sake of consistency. The Godless Shrine, well, those little lands empty your wallet faster than if you cut a hole in a water bed.

Not entirely true, there are a lot of Tier 1 Tron decks (Such as the normal Izzetron, for example.).
Compulsive research might be better than the Careful Consideration, but you get to see less cards and still end up with the same no matter how you play it. From FS, a Foresee might help the deck, as it lets you dig through six cards if you put the scryed ones on the bottom. An Ophidian Eye could also be beneficial, though since winning with Niv-Mizzet isn't the goal of the deck it's not needed.

Outside of Whisper's of the Muse you don't have any extra card drawing. So Niv-Mizzet is only for a nice size attacker then?
Could throw in Ophidian Eye as an alternate way to mass-deal some damage. The deck feels a little too reactive. By that I mean, the entire counterbase is relying on your opponent doing things that you can counter. And the turns you drop the Djinn, Niv-Mizzet or the pheonix you're likely going to be open unless it's extremely lategame.
Too many counters, not enough answers.

May as well toss in Ophidian eye. The mana might be a bit low, adding a few more would probably help you out.

And there's no reason to have Eye of Nowhere in the deck over Boomerang, since you don't have anything that needs sorceries or anything that needs Arcane.

Niv-Mizzet's my favorite guild leader of all time!

Ok, so far the Judge Unworthy are just plain useless to the deck. They're getting replaced with Wrath of God.

Also, I need to come up with a better name.

Looks good. Should think about throwing in Synod Sanctum for the shackles. If you take something with the shackles, you can remove it from the game and take another next turn. When your opponent is out of creatures, just tap 2 and get them all back on your side.

Well Lava Axe is a 5 to the face while Lightning Axe is 5 to a creature. This is a Burn to the Face deck, so the Lava axe will win over the Lightning Axe.

And why not put up a sub-par deck I can own? I'd prefer to put a deck up I have all the cards for than make a deck only Bill Gates could afford and hear comments on how awesome it is.

Extirpate is alright maindeck, just not taking up 4 slots. I'd reduce the number to 1 or 2, and put any extra in a sideboard.

As for Shimian Specter, well, if they don't have a hand then he's just a beatstick like all other specters. And yeah, once their hand is nuked Megrim is officially null and void. Maybe an Underworld Dreams would be suitable, the cost is essentially the same as megrim since your entire mana base is black.

The WoG's seem a little... counterproductive for a heavily creature-based deck like this. Though I guess it's neccesary if you get outcreatured.

Glare of Subdual would probably love this deck.

Looks like it might need more land.

Heh, throw in an Acadamy Ruins. Get yourself going with the Mindslaver lock. ;)

I'd cut one or two of the Circu, a lot is good for consistency but it's a dead card in multiples. And you should throw in some counters, for whatever they got to draw in their opening hand. =D

Should add in Flames of the Blood Hand. Gets past anything like COP's and prevents some problematic lifegain. "Beacon of Immortality? I don't think so. Take 4 damage."

Seething Song, Rite of Flame.

Well if your opponent is running basics then you're boned.

I know this isn't likely to happen in a serious tournament setting, but still. Maybe Terramorphic Expanse would be useful, if for nothing other than adding some power to a 'vore when you play it?

Sudden Shock might be interchangable with Fiery Temper... you lose the split second but gain some good synergy with Jaya.

Hate to run headfirst into it at an FNM. Though it would be a nice change from the B/W decks that almost everyone was running last time I went. x.x

Well Haunt creatures remove themselves from the game, so they sure can't be used with Debtor's Knell...