Huh, this can sound nasty... I will throw lots of rocks (imagine the rocks as figurative unbalances this card may have) and I will enjoy seeing how you deal with them, both if you evade them or get hit in the head with them 
1- I use this with fractal and Light Dragons (6xMartyr 6xFractal 6xLight Dragon, some pillars/towers/pends, Mark of Whatever, only a Duo). I play my upped Martyr, then fractal it, then... Well, I play all of them and after the first fractal, fractalling dragons gets more and more fun. Seem a bit too powerful, mainly with upped Martyr.
2- What happens if the top card in my hand is a targetting spell? Like Fire Bolt... Or if it's a Spark? I guess it dies instantly...
3- It's hard to see a non-casual use of the passive ability. I won't pack this card just to play a random card of my hand (one I may not even want to use) once my hand is clogged. I see it more like the active ability is too cool, and the passive is "meh".
Anyways, I like the picture, love the concept, and it gives me sooooo many decktype ideas, like MartyrNovaBows with 3/4 cost creatures instead of current 2/3 cost NovaBows, or... well, that's all I've imagined yet 
I actually wouldn't complain if Zanz made this a new card in the game as it is now.
1. 6 Dragons? Those would clog up your Martyr fractals. If you had less dragons, it'd be too slow. At the fastest, it can't beat an Immolation rush, considering how expensive Fractal is (2 quanta per Martyr isn't much to scoff at, either, since they're not free and don't generate Light quanta). And, despite being slower than some rushes, there isn't much defense to put in there (compared to RoL/Hope), and it can be countered by the same things (Thunderstorm, Firestorm, Fire Shield, Pandemonium, Lobotomizer). After that I'm more interested in multiple sky blitzes per turn, which can be put in the same deck if you can fractal Martyrs fast enough.
Actually, I'll change the notes so that the cost can't go below 1, so that you can't spam drain-all skills and are still confined to duos, trios, etc.
2. Discarding occurs before your creatures attack, so you would summon the spark, it'd attack, and then it'd die. Since you can't target after you end your turn, I'd envision that targeting spells would just be used up from the hand and wasted, but not discarded. Alternatives include being able to target after you discard the Martyr but before your creatures attack and me changing this card so that the first creature/permanent is played.
3. In the Fractal Martyr/Dragon deck you mentioned, as long as you play all the Martyrs above the Dragons in your hand, you can fractal even when you have no Light quanta and discard a Martyr to play that Dragon. On the contrary, I believe that Martyr's passive ability cannot be used "casually" when you only have Martyrs in the deck because it requires building a deck to utilize the ability. Whether that's good or bad, who knows.
