Toph, the First Metalbender

Nontoken artifacts you control are lands in addition to their other types. (They don't gain the ability to {T} for mana.)
At the beginning of your end step, earthbend 2. (Target land you control becomes a 0/0 creature with haste that's still a land. Put two +1/+1 counters on it. When it dies or is exiled, return it to the battlefield tapped.)

Symbiote Spider-Man

Whenever this creature deals combat damage to a player, look at that many cards from the top of your library. Put one of them into your hand and the rest into your graveyard.
Find New Host — {2}{U/B}, Exile this card from your graveyard: Put a +1/+1 counter on target creature you control. It gains this card's other abilities. Activate only as a sorcery.

Amazing Spider-Man

Vigilance, reach
Each legendary spell you cast that's one or more colors has web-slinging {G}{W}{U}. (You may cast a spell for its web-slinging cost if you also return a tapped creature you control to its owner's hand.)

Peter Parker

When Peter Parker enters, create a 2/1 green Spider creature token with reach.
{1}{G}{W}{U}: Transform Peter Parker. Activate only as a sorcery.

Peter Parker // Amazing Spider-Man

Fire Lord Zuko

Firebending X, where X is Fire Lord Zuko's power. (Whenever this creature attacks, add X {R}. This mana lasts until end of combat.)
Whenever you cast a spell from exile and whenever a permanent you control enters from exile, put a +1/+1 counter on each creature you control.

Appa, Steadfast Guardian

Flash
Flying
When Appa enters, airbend any number of other target nonland permanents you control. (Exile them. While each one is exiled, its owner may cast it for {2} rather than its mana cost.)
Whenever you cast a spell from exile, create a 1/1 white Ally creature token.

Katara, Waterbending Master

Whenever you cast a spell during an opponent's turn, you get an experience counter.
Whenever Katara attacks, you may draw a card for each experience counter you have. If you do, discard a card.

Sokka, Lateral Strategist

Vigilance
Whenever Sokka and at least one other creature attack, draw a card.

Fire Lord Ozai

Whenever Fire Lord Ozai attacks, you may sacrifice another creature. If you do, add an amount of {R} equal to the sacrificed creature's power. Until end of combat, you don't lose this mana as steps end.
{6}: Exile the top card of each opponent's library. Until end of turn, you may play one of those cards without paying its mana cost.

Aang, Master of Elements

Flying
Spells you cast cost {W}{U}{B}{R}{G} less to cast. (This can reduce generic costs.)
At the beginning of each upkeep, you may transform Aang, Master of Elements. If you do, you gain 4 life, draw four cards, put four +1/+1 counters on him, and he deals 4 damage to each opponent.

Avatar Aang

Flying, firebending 2
Whenever you waterbend, earthbend, firebend, or airbend, draw a card. Then if you've done all four this turn, transform Avatar Aang.

Avatar Aang // Aang, Master of Elements

Ghost-Spider, Gwen Stacy

Menace (This creature can't be blocked except by two or more creatures.)
Whenever Ghost-Spider attacks, she deals X damage to defending player, where X is the number of attacking creatures.

Ghost-Spider

Flying, vigilance, haste
Whenever you play a land from exile or cast a spell from exile, put a +1/+1 counter on Ghost-Spider.
Remove two counters from Ghost-Spider: Exile the top card of your library. You may play that card this turn.

Gwen Stacy

When Gwen Stacy enters, exile the top card of your library. You may play that card for as long as you control this creature.
{2}{U}{R}{W}: Transform Gwen Stacy. Activate only as a sorcery.

Gwen Stacy // Ghost-Spider

Origin of Spider-Man

(As this Saga enters and after your draw step, add a lore counter. Sacrifice after III.)
I — Create a 2/1 green Spider creature token with reach.
II — Put a +1/+1 counter on target creature you control. It becomes a legendary Spider Hero in addition to its other types.
III — Target creature you control gains double strike until end of turn.

Ultimate Spider-Man

First strike, haste
Camouflage — {2}: Put a +1/+1 counter on Ultimate Spider-Man. He gains hexproof and becomes colorless until end of turn.
Whenever you attack, double the number of each kind of counter on each Spider and legendary creature you control.

Miles Morales

When Miles Morales enters, put a +1/+1 counter on each of up to two target creatures.
{3}{R}{G}{W}: Transform Miles Morales. Activate only as a sorcery.

Miles Morales // Ultimate Spider-Man

Katara, Water Tribe's Hope

Vigilance
When Katara enters, create a 1/1 white Ally creature token.
Waterbend {X}: Creatures you control have base power and toughness X/X until end of turn. X can't be 0. Activate only during your turn. (While paying a waterbend cost, you can tap your artifacts and creatures to help. Each one pays for {1}.)