Alright gang! I'm going to do something I never ever do around these parts, and ask for some help.
My local store is doing a "random commander" night. It consisted of pulling a commander from a box, and then building a deck around it. I love the idea of the event and would really like to participate. Unfortunately I pulled kazarov, sengir pureblood and I'm having a lot of trouble actually getting the deck to DO anything.
There are a lot of things working against this one. His cost is very high, he's in colors that can't interact with enchantments, he has no built in way to protect himself, and he's very dependent on my opponents actually having creatures. Edhrec doesn't have much of an offering for ideas, and he's in no way a popular commander.
A few of the ideas I was kicking around were:
aether flash - it nails every creature that etb's, stops some combos, and does what the deck wants to do. i could potentially mix in repercussion or death pits of rath. this all feels really kind of... cute, and not very competitive.
He is pretty awful, the only things I can suggest is trying to use Pestilence style effects and then trying to win with a big Chandra's Ignition with all the tutors black has. The only real advantage Kazarov has is commander damage out of nowhere, but it generally requires a ridiculous amount of mana. You could also just use him for the colours and try to assemble a combo kill instead, like infinite mana into Exsanguinate or something.
I would just say in all honesty just ignore your commander for the most part, if you actually want a competitive deck.
The thing that he is 7 mana, so he only going to represent late game. He also requires a lot of mana to activate his ability, so again late game type of stuff.
So I would build a destroy everything you can type deck that you'd find more helmed by Mogis, God of Slaughter normally. What you can do is look to just keep removing the board as much as you can, with the idea of going into the late game.
That way you can resolve Kazarov, Sengir Pureblood and actually have a shot at just removing whatever your opponents have left.
So if that makes sense don't really worry about the +1/+1 and going Voltron, as you're just going to fail time and time again. Somebody will have removal for the first attack. So then he cost 9 mana to cast, and good luck again. Instead you need to be patient and wait out everybody else removal, while clearing the board yourself until you have like 10+ lands in play.
Then you're really using the 3R ability to wipe out whats going on. It is possible to play some of the double damage cards like Angrath's Marauders or more risky Dictate of the Twin Gods. But that means he'll ping for 4 damage, which is more likely to kill as single shots.
You could look at Horobi, Death's Wail as a way of one shot creatures. Basilisk Collar can give Kazarov deathtouch for the same effect. But I'd be careful about playing cards too specifically around him, for the reasons I pointed out above. That is to say they will do nothing on their own, and 90% of the time, games will be played without him on the board. That is just science
I agree with darrenhabib, you could just build a pretty tight Rakdos deck with Kazarov there for colours. Building a deck around a high cmc Commander is a pretty terrible idea; the exception being when that high cmc commander is stupid powerful (e.g. Avacyn, Angel of Hope), and you have extra ramp to get them out early (e.g. Thran Dynamo, Gilded Lotus).
This is my attempt at a Kazarov hyper-budget deck (all cards <$1 TCGPlayer mid). It's not the strongest deck, but I think this is the most efficient way to build him. It works fairly well in more low powered metas. The general idea is to keep the board as empty as possible until you can start building up Kazarov, then start taking out people with something like Fling, Tainted Strike or Chandra's Ignition.