PhoenixStrategy:When you think about fire, the first fire creature that comes to mind is probably Phoenix. Phoenix summarized what fire has to offer with its decks. A high damage creature with low defense but can be reborn! Most of fire's creatures are high damage/low defense so the ability to be reborn is especially important for fire decks, since it offers a consistency of damage when up against a high CC deck that can normally counter fire decks.
An example of such a deck is:
Normally such a deck would be easily countered by heavy CC but the ability of phoenix to be turned to ash
when killed and be able to be reborn back to phoenix for just 1 fire quantum allows fire to launch such decks with high probability of winning.
When phoenix is unupgraded its synergy with fire is very high with either mono decks such as the above or decks around Immolation(chech above). But, on the other hand, its synergy with every other element is extremely low. Its relatively high cost of 7 fire quanta makes it difficult to be a part of any duo(or trio etc.) deck that doesnt have Immolation in it.
However, enter
Phoenix is a card that when upgraded its cost is vastly reduced and its stats are somewhat lowered. Now, normally this is a downgrade when it comes to mono fire decks but it skyrockets its synergy with other elements.
and their upgrades.
Minor Phoenix combines with those cards especially well. When unupgraded, phoenix can be used as a damage dealer in immolation decks as well as a fodder sometimes, but when upgraded, its fodder duties augment due to its low cost which makes the deck a lot faster.
Thanks to its low cost, and relatively high damage considering the low cost, one of the most famous decks around is Fractix.
Fractix is a very strong deck that uses phoenix to its fullest potential. Single CC is meaningless against this deck and even with mass CC you can just revive the phoenixes later. Its relatively fast and with some form of PC it has a very low ttw.
As for nova, every low cost high damage creature can be used as a part of rainbow, nova based decks. Such is the case for phoenix (only)when upgraded. Its not exactly perfect synergy, neither can you make extremely good decks when you base them towards just nova and phoenixes, but it gives another option whereas unupgraded phoenix doesnt.
In general, phoenix provides fire with a lot of different kinds of options, rush, control, duo possibilites. Both the upgraded and the unupgraded versions of the card serve different purposes thus giving fire a fresh air of versatility.