I would swap out 12 of the forest for Ursa's Mine / Power Plant / Tower. Maybe some Ursa's Factory for as well some extra 2/2's.
Permalink
Some burn spells would definitely help. Look at the decklist I think the biggest problem you'll run into is keeping yourself alive along enough to get the dragons on the board. Burn would help a lot, as would some smaller creatures.
I'd consider adding more mana acceleration. At least a full set of 4 Seething Songs and maybe some Rite of Flame's. Might also want to consider some artifacts that can produce red mana, there are plenty to choose from.
Forgive me if I'm just missing it, I'm not always that good at seeing card combo's, but other then getting a high enough storm to cause your opponent to mill himself to death with Brain Freeze, or possibly a massive Stroke of Genius, how does this deck win? Or is the point simply to be as annoying as possible?
If you're looking to build a black, anti-sliver deck I'd say that you fight slivers with slivers. Put 4 Plague Sliver in the deck. It's a 5/5 for 2BB that basically says "All Slivers have 'At the beginning of your upkeep, this permanent deals 1 damage to you.'" Use that with some Dark Rituals and maybe some extra draw or search your deck cards, sure you'll take 1 damage per turn but your friend will be taking a lot more, he'll kill himself with his own slivers.
Excellent idea's, I'll definitely be updating the deck with them.