Combust
x4
1
Grenadin Drone
x4
1
Scrap Hound
x4
2
Combustion Cell
x3
2
Devour
x4
2
Into the Furnace
x4
3
Assembly Line
x4
3
Ixtun Merchant
x4
3
Madness
x4
3
Rally
x2
3
Ravenous Thornbeast
x4
4
Mazag, the Waking Terror
x2
5
Obrak, the Feaster
x2
5
Powderkeg Rider
x3
Fire Sigil
x6
Shadow Sigil
x11
Crest of Chaos
x2
Granite Waystone
x4
Stonescar Banner
x4
View Deck on Shiftstoned
You really want the 2 cost 2/1 grenadin that makes another 1/1 when he dies. It fits into your theme of saccing units
If you're using obrak, you may want to conisder dark return. It has a powerful synergy with destiny that shouldn't be overlooked.
I've never been impressed by powderkeg. I'd cut him as soon as you're able to afford more of your legendaries, or you have a gearcruncher. I think crunch would be a solid topend for this deck.
Also, you definitely want more crests.
More copies of scraptank would also be great.
I'm not thrilled with the warhelm in your market. You may want to cut it for some removal. Imo Obliterate is great because it gives you some reach and kills alot of things in the meta