Phoenix

Tips

 * Since most of Phoenix's abilities cost health to activate, health regeneration and strength boosting items should be a top priority. Urn of Shadows, Mekansm, Pipe of Insight and Heart of Tarrasque are good examples of such items.
 * As such, health regeneration items are a better choice than those that simply increase health, like Vitality Booster and Rod of Atos, as simply increasing health will make your health percentage consuming abilities much harder to maintain.
 * Since the only thing that can kill the Supernova are auto-attacks from Heroes, it's best to prioritize a Shiva's Guard as your first or second major purchase, as its passive attack slow works during your ultimate.With a bit of timing, you can also use Shiva's while Icarus Diving for a long ranged AOE disable.
 * Buying Eul's Scepter of Divinity can sometimes be a good investment, as you can still Sun Ray while under the effects of Eul's, and you can use it while diving to disable an enemy from a long distance. Do note, however, that the mana regeneration bonus is almost wasted unless you plan on spamming fire spirits and sun beam, as Phoenix relies more on health rather than mana.
 * Fire Spirit's attack speed reduction is great to mess up the enemies' last hits. Also, if used right before Supernova, it will make killing the sun harder.
 * Phoenix can be used both as a semi-carry and a support. If going for the former, take the mid lane and buy items to make you harder to kill. If you're supporting, consider going for cheap healing items such as Tranquil Boots, Urn of Shadows and a Mekansm.
 * You can go to the area around Roshan's pit and use Sun Ray to quickly and safely check if the enemy team is fighting Roshan.
 * Should you discover the enemy team inside the pit, have your team follow you, use Icarus Dive into the pit then use Supernova. If they choose to kill Roshan first, they may risk getting damaged heavily and stunned afterwards, during which your own team may get an upperhand. If they do decide to kill you first, then your team may kill Roshan themselves instead, or simply finish what your Supernova started.


 * You can give your team a significant initiation advantage by flying over the enemy team with Icarus Dive and rapidly covering the area in Fire Spirits while you are doing so. Fire Spirits will be easier to land from close proximity, but their high range can also allow you to hit spread-out team members. After the enemy team's movement and attack speed has been slowed, activating Supernova in the middle of it will both increase its chances of survival and its potential to inflict its damage and stuns effect.
 * In this combo the placement of your ultimate is very important. If you are confident about your team's follow-up, you may be able to soak up some extra damage before using your ultimate, thus relying on your team rather than your own short-lived disables to protect the Supernova. If you're less confident, you can continue the Icarus Dive to a point where Supernova can still affect some enemies, but to eliminate it the enemy heroes will have to (slowly) run towards you and your team and ignore the latter if they still intend to focus you. If you're not confident at all, you can resume support with your Sun Ray instead of using Supernova since the Icarus Dive will return you to your original position by default.
 * A Sun Ray that is about to run out can be added to this combo to inflict some extra damage during the Icarus Dive, which can give Phoenix a fast and fluid transition from artillery support to initiator/followup-initiator to seize opportunities. The combined health loss and cooldowns from all three abilities make him more dependent on the success of his Supernova to stay relevant for the fight however. Your combo can also be extended during the Icarus Dive with items such as Heaven's Halberd or Shiva's Guard which are not only most effective in close proximity to the enemy, but also further boost the survivability of your Supernova, which is why they can end up being more important for survivability than a Heart of Tarrasque for example.


 * If you want to play more aggressive in the midgame, consider putting skill points into Icarus Dive and Fire Spirits first and building a Veil of Discord to boost the damage of these abilities and your Supernova. Stat-wise Veil of Discord will also grant you some much-needed health regen and armor and a few stats across the board. Picking up the Null Talisman component first will improve your offensive lane presence because its mana pool and regeneration benefits let you use Fire Spirits a bit more liberally, while choosing the Helm of Iron Will component from the sideshop first instead will give you more defensive lane staying power by increasing your survivability and mitigating the HP cost of your abilities.
 * Magic Stick and Magic Wand are even more effective on Phoenix than most other heroes because his abilities cost both HP and mana, decreasing scenarios where you only use the items to gain just enough mana for casting an ability.