Sire of Insanity will steal your lunch money and then use it to buy pornography and sneak the pornography in your locker and tip off the principal so you will get suspended and your mom will take away your Playstation. He is a jerk with the Midas touch and he does not fuck around. There is not waiting until he dies or until your next upkeep. No, he makes everyone lose their hand immediately while leaving his beefy body around to bully all the utility creatures on the board. Sire really punishes slower decks and if you are able to accelerate him out early could be quite devastation at bringing the game to a standstill while everyone is in top deck mode. Granted if people are playing graveyard recursion you might end up helping them more than hurting them, but you can always play graveyard recursion yourself or be packing a fair amount of graveyard hate. He is powerful and in the right situation can net you a huge amount of card advantage, but expect for your opponents to be unhappy if you play with him.
4. Master of Cruelties
If Sire of Insanity is the school's worst bully, then Master of Cruelties is the kid that he is afraid of. Master of Cruelities is that kid that is lighting matches in the hallway and always talking about how he loves the smell of fire. He has never shared in his life, not even in Kindergarten, he has no concern for the well-being or feelings of others and his sole motivation in life is causing destruction. You have no doubts in your mind that he will end up in prison before the age of 18. Voracious Cobra is already quite a potent card in EDH at scaring away opposing attackers or getting in for damage and this is a powerful upgrade for only one mana more. Except for a small subset of creatures like other first strikers or indestructible creatures, Master of Cruelties will be able to kill anything in combat and survive, yet it is essential for your opponents to throw their creatures away and block because they will often be taking 20+ damage from one hit from this guy. Being at 1 in a multiplayer game is one of the worst strategic positions you can be in since it makes you so vulnerable and forces you to play defensively to keep yourself alive. And lord have mercy if you equip a whispersilk cloak to him. Despite being a jerk of the highest magnitude and putting a huge target on your head, Master of Cruelties is insanely powerful and probably worth the risk.
3. Teysa, Envoy of Ghosts
Full disclosure: I have built a Teysa deck that was inspired by my Zuberica deck and although it a bit of a good stuff deck and still needs some work, I'm already quite happy with its power level and fun factor. Although since seven mana is a steep price to pay for a general, Teysa might be better as an inclusion in your 99 cards than as your commander, but I think she still has a lot of potential as a general. Also, despite having the built in protection from creatures which is an awesome ability to have on a commander, it is unfortunate to have Teysa killed by a wrath or spot removal right after you play her and then have to get up to 9 mana to recast her in colors that don't have much ramp. However, if Teysa does stick around she is amazing at stabilizing your board and discouraging people from attacking you. She can already block about any ground creature and live but also kills any creatures that do get through to you. Who will want to attack into Teysa and lose all their creatures unless they can kill you that turn? Meanwhile since your defenses are built up you can still be attacking with unblocked Teysa each turn and she wears equipment quite well. It is a rare card that can play defense so well, while also being a solid contributor on offense.
2. Pontiff of Blight
Extort is quite powerful in multiplayer and this is most powerful extort card from multiplayer that Wizards printed. Given a decent number of creatures on the board, this makes every spell you play have an exsanguinate kicker. All this damage and lifegain will add up quickly and allow you to play defense with all of your creatures while draining everyone out turn after turn. This guy might seem unassuming, but, in most cases, is one of those creatures you have to kill right after it hits the board if you don't want that player to run away with the game.
1. Debt to the Deathless
Exsanuinate 2.0. Yes, please. Sure it is much slower and more mana intensive, but once you hit seven mana this is simply better for the price than exsanuinate and the upside just gets better and better from there. From the fact that it plays so well with extort and that it simultaneously helps you kill your opponents while gaining you so much life, I expect this card to see a lot of play as a finisher in grindy, long-game decks.