I have been having a lot of fun and success with this deck, got me from diamond 3 to diamond 1.
Basically, play lots of minions and sacrifice them to your bloodrite kalis. Sometimes this is enough to win as you can get 10/10 or higher kalis. If your kalis is destroyed, use smugglers stash to bring it back with some pals and play it again. It will keep the stats from the last sacrifice so each time you bring it back it gets bigger and bigger.
Cards like combust and madness are used to deal with opponents threats, dont forget you can sacrfice the creature you steal from madness with any of your sacrifice cards (Kalis, devour, combust).
Other Cards to Consider: Scheme: Adds more consistency for drawing your Kalis and Stashes, a little expensive for the power cost though.
Memory Dredger: Very powerful card if you can get it to hit, one problem is it has 2 shadow requirement so the powerbase would need to be drastically changed. Another problem is it is the only creature worth killing in the deck, so most opponents will be saving their removal the whole game and it is very rare that this guy hits.
Edit 1:
-3 Memory Dredger, -1 Scheme, +4 Talir's Favored, powerbase changed. Memory dredger was getting removed too often as it was the only creature worth removing in the deck so oppoents would be sitting on all their removal cards. There was also a lot of clunky power hands where all the lands would come into play depleted, so with memory dredger gone we can now afford to run a lot more time sigils (Dredger was the only double shadow requirement card).
Edit 2:
-2 Scheme, -2 Talir's Favored, +4 Torrent of Spiders, -2 Time Sigil, +2 Stonescar Banner. Thanks to Amph3's discovery, Torrent of Spiders is actually nuts in this deck, often generating 3+ units that are great blockers. Cut 2 favored and changed the powerbase a bit to be a little less heavy on time to more consistently get that Fire/Shadow requirment met.
Combust
x4
1
Grenadin Drone
x4
2
Dark Wisp
x4
2
Devour
x4
2
Quarry
x4
2
Talir's Favored
x2
2
Temple Scribe
x4
3
Amber Acolyte
x4
3
Assembly Line
x4
3
Bloodrite Kalis
x4
3
Madness
x4
3
Torrent of Spiders
x4
5
Smuggler's Stash
x4
Fire Sigil
x1
Shadow Sigil
x1
Time Sigil
x7
Seat of Chaos
x4
Seat of Impulse
x4
Seat of Mystery
x4
Stonescar Banner
x4
View Deck on Shiftstoned
I haven't forked out for the Quarry card yet (it's campaign only right?) so substituted as mentioned by others with Scheme and Xenan Augary. I am also down on 1 Kalis and 2 Torrents so I added a couple of Recogulator (good card to sacrifice on a block as your still increasing your unit quantity) and a Dark Return (good for bringing back some low cost units whilst waiting for the draw.
-You get to attack with the creature. This is huge. When playing against slow decks it is best to play this deck aggressively. Getting in an extra 5 damage from a Sandstorm Titan or 6 from a Cirso will help get you closer to finishing off your opponent, and sometimes it will help break a relic weapon that you otherwise couldn't deal with due to big blockers on your opponents side.
-Madness hits any creature, and you get void triggers. One of my favorite targets for Madness is Makto, not only does it remove your opponents Makto, but you get your own with Destiny in the top 10 cards of your deck since Makto dies while you control him. This is also works for DawnWalker and any other revenge units. Madness also has no requirements on the creature you target, unlike Annihilate and Banish.
-Madness saves you 1 unit for your sacrifice effects. If Madness were another removal card your combust/devour would just be eating one of your creatures instead and Kalis will often be 2/2 less in strength. This isn't to big of a bonus, but it is significant and sometimes can mean the difference between squeezing in the last bit of damage vs a control deck or surviving burn from your opponent thanks to the 2 extra armor from Kalis.
As for Madness being slow, if everything is going well with your draw this shouldn't be a problem. Ideally you are using up most or all of your power each turn with this deck, developing minions or drawing cards.
I could see adding in Annihilate/Banish if you are feeling like you need more efficient removal or running into issues with relics. I just wouldn't cut the Madness (Mwha mwah hahaha), perhaps grenadin drone or Assembly line is what I would cut.
If you do test out any changes with Annihilate/Banish and find that they are improving the deck a lot let me know! I would take another look at them, but right now I'm not so inclined to add them in.
I have no Quarry so I'm running x3 Torrent of Spiders and they are super good so far.