I dunno, with the enormous amounts of dragons in EDH, Karrthus is a 3-turn kill with haste that gets all dragons on the field for you permanently, untaps them, and gives them haste. Especially dragons that others have stolen. I once stole someone's general (Vorosh, the Hunter) and killed them with it...
I have a friend who runs Thraximundar, and he's okay, good color combo, but he dies to Tajuru Preserver, something that I have seen 5 people run to date in EDH (I don't, I'm fast enough to kill your before you get the necessary 7 mana, a problem with RBU color EDH decks). I run Phthisis just for stuff like him, to blow him up and give you 12+ damage to the face. (Wheheheh, I blew up a 35/35 Omnath General once, its owner didn't have any instant-speed outlets for the mana, so he died.)
I recently tried out a funky list that I came up with: (It didn't work at all, so don't bother to try to improve)
Basically it just ramped up to the obnoxious P. Hydra/Etched Monstrosity and Hex Parasite/Melira, Sylvok Outcast combo... (Melira creates a Phyrexian Hydra that prevents ALL damage done to it, and an Etched Monstrosity that comes in as a 10/10 for 5. Hex Parasite can fill a similar role by removing counters placed on them while pumping itself, and it can remove a counter from Garruk to transform him.)
It was a bit slow, Culling Dias provided draw support while removing the Viridian Emissary and Solemn Simulacrum.
It won occasionally, but it was too slow...
I thought it was funny, though.
I have a friend who runs Thraximundar, and he's okay, good color combo, but he dies to Tajuru Preserver, something that I have seen 5 people run to date in EDH (I don't, I'm fast enough to kill your before you get the necessary 7 mana, a problem with RBU color EDH decks). I run Phthisis just for stuff like him, to blow him up and give you 12+ damage to the face. (Wheheheh, I blew up a 35/35 Omnath General once, its owner didn't have any instant-speed outlets for the mana, so he died.)
I recently tried out a funky list that I came up with: (It didn't work at all, so don't bother to try to improve)
Healer Sweep (GB Combo)
3 Viridian Emissary
3 Solemn Simulacrum
3 Cathedral Membrance
3 Melira, Sylvok Outcast
2 Phyrexian Hydra
2 Etched Monstrosity
3 Hex Parasite
3 Birds of Paradise
1 Massacre Wurm
Creatures: 23
3 Doom Blade
2 Prey Upon
3 Rampant Growth
4 Culling Dias
Spells: 12
3 Garruk Relentless/Garruk, the Veil-Cursed
Planeswalkers: 3
4 Woodland Cemetery
13 Forest
5 Swamp
Lands: 22
Cards: 60
3 Viridian Emissary
3 Solemn Simulacrum
3 Cathedral Membrance
3 Melira, Sylvok Outcast
2 Phyrexian Hydra
2 Etched Monstrosity
3 Hex Parasite
3 Birds of Paradise
1 Massacre Wurm
Creatures: 23
3 Doom Blade
2 Prey Upon
3 Rampant Growth
4 Culling Dias
Spells: 12
3 Garruk Relentless/Garruk, the Veil-Cursed
Planeswalkers: 3
4 Woodland Cemetery
13 Forest
5 Swamp
Lands: 22
Cards: 60
Basically it just ramped up to the obnoxious P. Hydra/Etched Monstrosity and Hex Parasite/Melira, Sylvok Outcast combo... (Melira creates a Phyrexian Hydra that prevents ALL damage done to it, and an Etched Monstrosity that comes in as a 10/10 for 5. Hex Parasite can fill a similar role by removing counters placed on them while pumping itself, and it can remove a counter from Garruk to transform him.)
It was a bit slow, Culling Dias provided draw support while removing the Viridian Emissary and Solemn Simulacrum.
It won occasionally, but it was too slow...
I thought it was funny, though.