Interesting that the element of the highest damage needs more
.
That being said, I think this fit's the theme of fire pretty nicely. Fire is all about dishing out untold amounts of damage, in short order. The high cost to play still might not be balanced though. First off, Fire has Cremation and could play this extremely early without too much difficulty. And if you had to sacrifice 2 Phoenixes to do it, you still have 6 damage on the field from the ashes. Having an upkeep cost would make that much more difficult. Also, only affecting your creatures seems to be a bit... off. I think that at least the unupgraded should target all fire creatures, but like Eclipse, I think it should effect both. Also, it should not be allowed to stack, especially if it's just a high cost, even at an upkeep of 3, 6 wasted pillars isn't a big deal because for each pillar wasted, you gain 1 point of attack to any creature you have. Make them Phoenixes which are hard to kill, and heal you for 13 if LSed and you've got a pretty darn menacing deck.
In short, I think that having it be a 6
,
upkeep would combine the ideas of Flooding and Nightfall into a card that is thematic of Fire. They would be unstackable and effect both players. The upgraded one could just target your creatures I suppose. That's my take on it, but I'm not the best at balancing such things.