Grenadin 3 2fs

This is very similar to my Grenadin 3 f deck.

I splashed shadow for a bit of life gain through Devour
If you don't have the Crests of Chaos you can replace them with shadow sigils. <-- This is what I did so my deck would be faster. Besides, I only need 2 fire influence and 1 shadow influence to basically play half my deck.

Card highlights:

With the addition of Combust I don't need Into the Furnace.

I considered Combustion Cell , but this deck doesn't need more power as its maximum power cost is only 3. It's a cheaper way to sacrifice units than Brimstone Altar, for sure, but since you should always use these two cards after you attack, it's better to just save a power for brimstone. Feel free to add it to your decks and try it out though! I would only run combustion cell if I wanted Scraptank or Gearcruncher.

Card timing:
Brimstone Altar: This should be used after you attack to get maximum damage. I also only use it as a finisher, but if you suspect a board wipe by all means use it. It could also be used to remove the opponent's avatar aegis, but it's not a good idea. Just use a tripwire grenadin or something. 2 damage being negated is a pretty big (at least to me) setback. I mean, there's lifesteal...

Devour: If the enemy unit has overwhelm and is attacking and you use this card, all of the damage will go through. Just a warning.