Most folks play Sparkmage to maximize damage dealt to the opponent avatar using their Air threshold ability. To me, that's the correct way and main priority when playing that avatar to get the most out of "why" you have chosen to play it. There are great spells like browse, lightning bolt, thunderstorm, and mobility and card draw galore. Whether you play spell-heavy control, recurring evil presence + spirits, just plain aggro, or suit him up with artifacts and treat him like a scrappy little battlemage, there are fairly limited spells to select from but many viable tempos/strategies to play Sparkmage, whether youre heavy on minions or spells.

Now we have Flamecaller. I don't think we are supposed to approach Flamecaller the same way, as projectiles are harder to make relevant damage to the enemy avatar, and we dont benefit from threshold of magic and aura spells, only minions... and even THEN we have to get them out AND wait for them to die. To maximize the payoff for playing Flamecaller, I think this means we do have to play a bit differently. We can still be aggressive or controlling, but we definitely want all our minions (however many we choose to run) to have some amount of fire threshold, and need to emphasize mobility and card draw. The interesting puzzle to solve is: What that projectile actually does is largely dependent on keeping the row between avatars totally clear (its a weapon to win the game) or expecting that it will always hit a minion (and never expecting to do big damage with it, but use it regularly, since it will totally clear out our cemetery) I've opted for getting the most out of the deck by assuming the latter, and making the main strategy thus:

Give Flamecaller a dagger, and trade every minion of our own with one of theirs, so we always have a laser that kills *another* enemy minion, clearing the way for a new one of our own, rinse and repeat. Since I always want one dagger on my avatar, I want minions that ideally would like wearing them also.

Notable Cards:

Dragonettes and Kobolds are the best examples of friendly dagger bearers.

Twinnax Berserker seems like a fun minion to play in a deck where we don't *really* mind throwing our minions away (*1), but they have a huge upside of being able to do more if they don't have to die right away.

Leaning into this, we play crown, skull, and mask, in hopes of trading up with our little guys against the big earth minions.

Since we are running multiple effects that require we MUST attack, Hillock Basilisk is almost entirely necessary so we don't get screwed by those "must attack" effects and leverage them on our own terms.

Air for ramp and mobility complete the Sparkmage Imposter strategy, because getting angles and drawing cards are both necessary for utilizing the projectile.

Notable Combos:

If you get a crown on a twinnax berserker or a kobolds, grappleshot or critical strike can wrap up the game super quickly.

Spear of Destiny is so good because we fear big monsters, but "dont mind" if the opponent goes over and wastes their turn using one of their minions to throw it back.

Last Word: This is an experiment, there are still lots of flex spots as one of the primary goals of this deck was to use some cards I wasn't using, and create a deck with every Avatar. Hit me up if you have thoughts!

@TheMurderBurger

*1: Aramos Mercenaries has never felt like a good enough card to me. It easily could find a spot in a deck like this IF (big if) you run LOTS of minions. But I really dont want to throw a minion into the cemetery for another lethal laser most of the time and then go 2-4 turns without finding another one, so my build would need to change a bit to entertain adding them.