From LSWiki

Contents 1 Bonding Requirements 2 Known Abilities 2.1 Petting the familiar 2.2 Attribute Modifications 2.3 Specialty Bonuses 2.4 Charms 2.5 Additional Bonuses and Powers 2.5.1 Traits granted

Bonding Requirements

"Resilient form" and "fiery spirit" - it appears that some combination of Courage, Resilience, Steadiness, and possibly Pain Tolerance meets the first requirement. Discipline and Tenacity may be other alternatives, but were not required (bonded at zero skill in one case). A large amount of Fire Affinity sufficed for the second requirement, although Twilight has stated there are other means of satisfying that. Phaethon are the obvious choice for bonding this familiar easily, although there are certainly many other combinations that can work just as well.

Known Abilities

The majestic phoenix is an enchanted avian beast that can be found in Darkhold's dungeon, or possibly other places. It is a ferocious combatant with its deadly beak and claws, and it has wings made of fire, with which it can also attack. It breathes air, and the flames surrounding its body emit significant light. The phoenix is magificently agile and tough, with a large amount of resistance to mundane damage, and when struck it inflicts fire damage on contact. It has a carnivorous diet.

NB: the light emitted by the phoenix can be a significant downside for a character with any degree of light sensitivity.

Petting the familiar

You pet Tempest with your bony right hand.
Your bony right hand is singed by contact with Tempest's orange fire, though 
you are largely unaffected by the attack.

This inflicts a small amount of fire damage on contact. Note that with enough fire affinity, this will eventually result in a very minor heal, although presumably at some cost to the familiar.

Attribute Modifications

The phoenix familiar grants its consort a large bonus to constitution and charisma.

Specialty Bonuses

Bonus specialty degrees and access are provided as follows:

• Fire Affinity
• Biofeedback
• Recuperation
• Regeneration
• Stamina
• Anatomy
• Diagnosis
• First Aid
• Pyromancy
• Empathy
• Supernal Durability NB: no bonus specs seem to be granted here, but it is well worth noting just the same
• Channeling
• Sky Fieldcraft

Charms

• Urge

Shortly after:

• Call
• Send
• Kinsee

At "fairly healthy" bond strength:

• Convert spell points into Elemental Fire resource energy
• Renew, a self-only healing effect

Additional Bonuses and Powers

At "fairly healthy" bond strength, a new attack maneuver called "Gout of White-Hot Flame" is granted. The attack requires elemental fire energy obtained by the Convert charm, also granted at the same tier.

Traits granted

At "fairly healthy" bond strength, the consort is granted the Luminescence trait, which grows with bond strength. Be aware that for a character with any degree of light sensitivity, this is a significant liability rather than a benefit.