Suggestions you might consider are Malfegor, Stronghold Rats, Chronozoa, Vampire Hexmage, and Deadeye Navigator, Liliana's Specter, Spiteful Visions, Hex Parasite, Harvester of Souls, Tyrannize and if you feel your losing too much life, Exquisite Blood

I'd recommend anything with annihilator, especially Eldrazis. I run Pathrazer of Ulamog, It That Betrays and Artisan of Kozilek in my Thrax deck and they can back me up when someone decides to give their creatures protection from these colors. Also, I've found that Thrax is very vulnerable to enchantments so get Nevinyrral's Disk so you have some backup in case you don't draw or don't have enough mana for Nicol Bolas.

You also need some equipments. If your goal is to be annoying, you will undoubtedly have a huge bullseye on your back, and you need to protect your general before he gets killed so many times that he's nearly impossible to resummon. Also, your general is almost guaranteed to be blocked as much as possible so it's a good idea to give him trample. Cards that can do this include Lightning Greaves, Akroma's Memorial, Whispersilk Cloak, Swiftfoot Boots, and Loxodon Warhammer. Also, get Counterspell, AEtherize, Undermine, or other blue negators. Blue is a very strong defensive color, and since your opponents are bound to try and paralyze your deck, it's good to take advantage of this and retaliate.

Thanks man, I do need some equips. I'll play a few games and see if I get enough mana to cast the eldrazi. Thanks.

Check out my main EDH Deck, It sounds like something similar to what you're looking for. do-it-before-i-do-it-for-you

Thank you for your comment on my deck, I also like yours, I was going to ask how Bitterblossom ends up working, does it seem to pay off or does it hurt you in the end? :O I am very interested in this card.

Also a +1 from me. Go Grixis!

Seriously? Bitterblossom is a bomb of a card, two mana and.. one life every round for a creature is amazing.. especially when you play it with cards like Falkenrath Noble or Blood Artist and your average sacrifice outlet like Bloodthrone Vampire . in fact.. even by itself its a heavy threat, flying creatures for 2 mana are nothing to mock.