Fire Lord Azula

Firebending 2 (Whenever this creature attacks, add {R}{R}. This mana lasts until end of combat.)
Whenever you cast a spell while Fire Lord Azula is attacking, copy that spell. You may choose new targets for the copy. (A copy of a permanent spell becomes a token.)

Ozai, the Phoenix King

Trample, firebending 4, haste
If you would lose unspent mana, that mana becomes red instead.
Ozai has flying and indestructible as long as you have six or more unspent mana.

Vedalken Orrery

You may cast spells as though they had flash.

Sozin's Comet

Each creature you control gains firebending 5 until end of turn. (Whenever it attacks, add {R}{R}{R}{R}{R}. This mana lasts until end of combat.)
Foretell {2}{R} (During your turn, you may pay {2} and exile this card from your hand face down. Cast it on a later turn for its foretell cost.)

Leyline of Anticipation

If this card is in your opening hand, you may begin the game with it on the battlefield.
You may cast spells as though they had flash.

Electro, Assaulting Battery

Flying
You don't lose unspent red mana as steps and phases end.
Whenever you cast an instant or sorcery spell, add {R}.
When Electro leaves the battlefield, you may pay {X}. When you do, he deals X damage to target player.

The Last Agni Kai

Target creature you control fights target creature an opponent controls. If the creature the opponent controls is dealt excess damage this way, add that much {R}.
Until end of turn, you don't lose unspent red mana as steps and phases end.

Etali, Primal Storm

Whenever Etali attacks, exile the top card of each player's library, then you may cast any number of spells from among those cards without paying their mana costs.

High Fae Trickster

Flash (You may cast this spell any time you could cast an instant.)
Flying
You may cast spells as though they had flash.

Kess, Dissident Mage

Flying
Once during each of your turns, you may cast an instant or sorcery spell from your graveyard. If a spell cast this way would be put into your graveyard, exile it instead.

Swiftfoot Boots

Equipped creature has hexproof and haste. (It can't be the target of spells or abilities your opponents control. It can attack and {T} no matter when it came under your control.)
Equip {1} ({1}: Attach to target creature you control. Equip only as a sorcery.)