Human Torch

At the beginning of combat on your turn, if you've cast a noncreature spell this turn, Human Torch gains flying, double strike, and haste until end of turn.
Whenever Human Torch attacks, you may pay {R}{G}{W}{U}. If you do, until end of turn, whenever he deals combat damage to an opponent, he deals that much damage to each other opponent.

Namor the Sub-Mariner

Flying
Namor's power is equal to the number of Merfolk you control.
Whenever you cast a noncreature spell with one or more blue mana symbols in its mana cost, create that many 1/1 blue Merfolk creature tokens.

Moon Girl and Devil Dinosaur

Whenever you draw your second card each turn, until end of turn, Moon Girl and Devil Dinosaur's base power and toughness become 6/6 and they gain trample.
Whenever an artifact you control enters, draw a card. This ability triggers only once each turn.

Mister Fantastic

Vigilance, reach
At the beginning of combat on your turn, if you've cast a noncreature spell this turn, draw a card.
{R}{G}{W}{U}, {T}: Copy target triggered ability you control twice. You may choose new targets for the copies.

Doctor Doom

When Doctor Doom enters, create two 3/3 colorless Robot Villain artifact creature tokens named Doombot.
As long as you control an artifact creature or a Plan, Doctor Doom has indestructible.
At the beginning of your end step, you draw a card and lose 1 life.

Captain America, Super-Soldier

First strike
Captain America enters with a shield counter on him. (If he would be dealt damage or destroyed, remove a shield counter from him instead.)
As long as Captain America has a shield counter on him, you and other Heroes you control have hexproof.

Quicksilver, Brash Blur

If Quicksilver, Brash Blur is in your opening hand, you may begin the game with him on the battlefield.
Haste
Power-up — {4}{R}: Put a +1/+1 counter and a double strike counter on Quicksilver. (Activate each power-up ability only once. Reduce the cost by his mana cost if he entered this turn.)

Wolverine, Best There Is

Unrivaled Lethality — Double all damage Wolverine would deal.
At the beginning of each end step, if Wolverine dealt damage to another creature this turn, put a +1/+1 counter on him.
{1}{G}: Regenerate Wolverine. (The next time he would be destroyed this turn, instead tap him, remove him from combat, and heal all damage on him.)

The Sentry, Golden Guardian

Flying, vigilance, indestructible
When The Sentry enters, target opponent creates The Void, a legendary 5/5 black Horror Villain creature token with flying, indestructible, and "The Void attacks each combat if able."

The Thing

Trample
At the beginning of combat on your turn, if you've cast a noncreature spell this turn, put four +1/+1 counters on The Thing.
Whenever The Thing attacks, you may pay {R}{G}{W}{U}. When you do, double the number of each kind of counter on any number of target permanents you control.

Captain America, Team Leader

Whenever another Hero you control enters, it gains vigilance and haste until end of turn. Put a +1/+1 counter on that Hero and a +1/+1 counter on Captain America.

Super-Skrull

Flying
{2}{W}: Create a 0/4 colorless Wall creature token with defender.
{3}{G}: Super-Skrull gets +4/+4 until end of turn.
{4}{R}: Super-Skrull deals 4 damage to target creature.
{5}{U}: Target player draws four cards.

Invisible Woman

At the beginning of combat on your turn, if you've cast a noncreature spell this turn, create a 0/3 colorless Wall creature token with defender and reach.
Whenever you attack, you may pay {R}{G}{W}{U}. When you do, target creature gets +1/+0 until end of turn for each creature you control and can't be blocked this turn.

Baron Helmut Zemo

Whenever you cast a black spell from your hand, Baron Helmut Zemo connives.
Boast — Exile any number of black cards from your graveyard with fifteen or more black mana symbols among their mana costs: Copy those exiled cards. You may cast up to three of the copies without paying their mana costs. (Activate only if this creature attacked this turn and only once each turn.)

Iron Man, Titan of Innovation

Flying, haste
Genius Industrialist — Whenever Iron Man attacks, create a Treasure token, then you may sacrifice a noncreature artifact. If you do, search your library for an artifact card with mana value equal to 1 plus the sacrificed artifact's mana value, put it onto the battlefield tapped, then shuffle.

Captain America, First Avenger

Throw ... — {3}, Unattach an Equipment from Captain America: He deals damage equal to that Equipment's mana value divided as you choose among one, two, or three targets.
... Catch — At the beginning of combat on your turn, attach up to one target Equipment you control to Captain America.

T'Challa, the Black Panther

Whenever T'Challa enters or attacks, create a tapped Vibranium token. (It's an artifact with indestructible and "{T}: Add {C}. This mana can't be spent to cast a nonartifact spell.")
Whenever you cast an artifact spell with mana value 4 or greater, put two +1/+1 counters on T'Challa.

The Incredible Hulk

Reach, trample
Enrage — Whenever The Incredible Hulk is dealt damage, put a +1/+1 counter on him. If he's attacking, untap him and there is an additional combat phase after this phase.

Bruce Banner

{X}{X}, {T}: Draw X cards. Activate only as a sorcery.
{2}{R}{R}{G}{G}: Transform Bruce Banner. Activate only as a sorcery.

Bruce Banner // The Incredible Hulk

Doctor Doom, King of Latveria

Whenever you discard one or more land cards, each opponent loses 2 life.
At the beginning of combat on your turn, target Villain you control gains menace until end of turn. It connives. (Draw a card, then discard a card. If you discarded a nonland card, put a +1/+1 counter on that creature.)

Attuma, Atlantean Warlord

Other Merfolk you control get +1/+1.
Whenever one or more Merfolk you control attack a player, draw a card.