I love Worldfire and other horrifically powerful cards with tremendous drawbacks, so have tried several times to build a Worldfire deck that works. Frankly, 9 mana is too much, and I would highly recommend finding a way to cheat it into play.
Spellweaver Helix is a strong card in a Worldfire Deck. Essentially, you want to imprint Worldfire and a damage spell onto the Helix. You then cast the same damage spell, putting it onto the stack. A copy of Worldfire is triggered due to Helix's ability, and will resolve first, putting your opponent at 1 HP. The damage spell will then resolve, finishing off your opponent.
Using this method, it is best to use a large number of loot cards (i.e. Faithless Looting or other draw+discard spells), so you can force your combo pieces into your graveyard.
If you do not feel like winning through combo, I might suggest looking into phasing. It's generally a terrible mechanic, but would protect your creature from Worldfire. You could also try to splash white for Oblivion Ring, and exile a creature with haste. This would return to the battlefield as soon as Worldfire removes the Oblivion Ring, giving you a finisher.
Currently, I have a casual goblin deck with a number of 1 drop haste creatures, several Skirk Prospector and Brightstone Ritual, and one copy of Worldfire (generally, the goblin mana-ramp is used to enable Banefire). It's a terrible card for the deck, but felt very thematically appropriate--my group and I focus on control/combo, and goblins fare poorly against pillowforts. There is something very goblin-like about nuking the entire playing field in a desperate attempt to win.
January 23, 2018 11:05 a.m.
January 23, 2018 12:47 p.m.
Of the new set, Release to the Wind might be quite good?
January 23, 2018 7:17 p.m.
Mizzix's Mastery is legacy legal btw. So you actually could curve out and win turn 3-4. Following this idea:
turn 2--> Seal of Fire or some other hasty 1-drop creature. You keep it 1 cmc co that you can lay out more than one if need be.
turn 3--> Wait for opponent's turn (end step of course), play Release to the Wind on one of your win cons from the previous turn.