Mossborn Hydra

Trample (This creature can deal excess combat damage to the player or planeswalker it's attacking.)
This creature enters with a +1/+1 counter on it.
Landfall — Whenever a land you control enters, double the number of +1/+1 counters on this creature.

Genji Glove

Equipped creature has double strike.
Whenever equipped creature attacks, if it's the first combat phase of the turn, untap it. After this phase, there is an additional combat phase.
Equip {3}

World Champion, Celestial Weapon

Double Overdrive — Equipped creature gets +2/+0 and has double strike.
Equip {3} ({3}: Attach to target creature you control. Equip only as a sorcery.)

Sidequest: Play Blitzball

At the beginning of combat on your turn, target creature you control gets +2/+0 until end of turn.
At the end of combat on your turn, if a player was dealt 6 or more combat damage this turn, transform this enchantment, then attach it to a creature you control.

Sidequest: Play Blitzball // World Champion, Celestial Weapon

Cabal Ritual

Add {B}{B}{B}.
Threshold — Add {B}{B}{B}{B}{B} instead if seven or more cards are in your graveyard.

Anthem of Rakdos

Whenever a creature you control attacks, it gets +2/+0 until end of turn and this enchantment deals 1 damage to you.
Hellbent — As long as you have no cards in hand, if a source you control would deal damage to a permanent or player, it deals double that damage to that permanent or player instead.

Sangrite Surge

Target creature gets +3/+3 and gains double strike until end of turn.

Grappling Hook

Equipped creature has double strike.
Whenever equipped creature attacks, you may have target creature block it this turn if able.
Equip {4}

Angrath's Marauders

If a source you control would deal damage to a permanent or player, it deals double that damage to that permanent or player instead.

Armorcraft Judge

When this creature enters, draw a card for each creature you control with a +1/+1 counter on it.

Hydra's Growth

Enchant creature
When this Aura enters, put a +1/+1 counter on enchanted creature.
At the beginning of your upkeep, double the number of +1/+1 counters on enchanted creature.

Bulk Up

Double target creature's power until end of turn.
Flashback {4}{R}{R} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Ascendant Acolyte

This creature enters with a +1/+1 counter on it for each +1/+1 counter among other creatures you control.
At the beginning of your upkeep, double the number of +1/+1 counters on this creature.

Fireshrieker

Equipped creature has double strike. (It deals both first-strike and regular combat damage.)
Equip {2} ({2}: Attach to target creature you control. Equip only as a sorcery.)

Darigaaz's Caldera

When this land enters, sacrifice it unless you return a non-Lair land you control to its owner's hand.
{T}: Add {B}, {R}, or {G}.

Kalonian Hydra

Trample
This creature enters with four +1/+1 counters on it.
Whenever this creature attacks, double the number of +1/+1 counters on each creature you control.

The Spear of Leonidas

Whenever equipped creature attacks, choose one —
• Bull Rush — It gains double strike until end of turn.
• Summon — Create Phobos, a legendary 3/2 red Horse creature token.
• Revelation — Discard two cards, then draw two cards.
Equip {2}

Doubling Cube

{3}, {T}: Double the amount of each type of unspent mana you have.

Rage Reflection

Creatures you control have double strike.

Sage of the Fang

When this creature enters, put a +1/+1 counter on target creature.
Renew — {3}{G}, Exile this card from your graveyard: Put a +1/+1 counter on target creature, then double the number of +1/+1 counters on that creature. Activate only as a sorcery.

Mountain

Deathbloom Ritualist

{T}: Add X mana of any one color, where X is the number of creature cards in your graveyard.

Runes of the Deus

Enchant creature
As long as enchanted creature is red, it gets +1/+1 and has double strike. (It deals both first-strike and regular combat damage.)
As long as enchanted creature is green, it gets +1/+1 and has trample.

Savage Lands

This land enters tapped.
{T}: Add {B}, {R}, or {G}.

Inquisitor's Flail

If equipped creature would deal combat damage, it deals double that damage instead.
If another creature would deal combat damage to equipped creature, it deals double that damage to equipped creature instead.
Equip {2}

Riveteers Charm

Choose one —
• Target opponent sacrifices a creature or planeswalker they control with the greatest mana value among creatures and planeswalkers they control.
• Exile the top three cards of your library. Until your next end step, you may play those cards.
• Exile target player's graveyard.

Arcane Signet

{T}: Add one mana of any color in your commander's color identity.

Attacking creatures you control get +1/+0 until end of turn for each other attacking creature.

Target player sacrifices an artifact or creature of their choice. Hit deals damage to that player equal to that permanent's mana value.

Hit // Run

Biogenic Upgrade

Distribute three +1/+1 counters among one, two, or three target creatures, then double the number of +1/+1 counters on each of those creatures.

Jaspera Sentinel

Reach
{T}, Tap an untapped creature you control: Add one mana of any color.

Gavel of the Righteous

At the beginning of combat on your turn, put a charge counter on this Equipment.
Equipped creature gets +1/+1 for each counter on this Equipment.
As long as this Equipment has four or more counters on it, equipped creature has double strike.
Equip—Pay {3} or remove a counter from this Equipment.

Psychotic Fury

Target multicolored creature gains double strike until end of turn.
Draw a card.

Spelleater Wolverine

This creature has double strike as long as there are three or more instant and/or sorcery cards in your graveyard.

Unnatural Growth

At the beginning of each combat, double the power and toughness of each creature you control until end of turn.

Blood Mist

At the beginning of combat on your turn, target creature you control gains double strike until end of turn.

Ziatora's Proving Ground

({T}: Add {B}, {R}, or {G}.)
This land enters tapped.
Cycling {3} ({3}, Discard this card: Draw a card.)

Sol Ring

Pyretic Ritual

Doubling Season

If an effect would create one or more tokens under your control, it creates twice that many of those tokens instead.
If an effect would put one or more counters on a permanent you control, it puts twice that many of those counters on that permanent instead.

Fangs of Kalonia

Put a +1/+1 counter on target creature you control, then double the number of +1/+1 counters on each creature that had a +1/+1 counter put on it this way.
Overload {4}{G}{G} (You may cast this spell for its overload cost. If you do, change "target" in its text to "each.")

Jund Charm

Choose one —
• Exile target player's graveyard.
• Jund Charm deals 2 damage to each creature.
• Put two +1/+1 counters on target creature.

Abnormal Endurance

Until end of turn, target creature gets +2/+0 and gains "When this creature dies, return it to the battlefield tapped under its owner's control."

Mr. Orfeo, the Boulder

Whenever you attack, double target creature's power until end of turn.

Pariah's Shield

All damage that would be dealt to you is dealt to equipped creature instead.
Equip {3}

Targ Nar, Demon-Fang Gnoll

Pack tactics — Whenever Targ Nar attacks, if you attacked with creatures with total power 6 or greater this combat, attacking creatures get +1/+0 until end of turn.
{2}{R}{G}: Double Targ Nar's power and toughness until end of turn.

Primordial Hydra

This creature enters with X +1/+1 counters on it.
At the beginning of your upkeep, double the number of +1/+1 counters on this creature.
This creature has trample as long as it has ten or more +1/+1 counters on it.

Dark Ritual

Darigaaz's Charm

Choose one —
• Return target creature card from your graveyard to your hand.
• Darigaaz's Charm deals 3 damage to any target.
• Target creature gets +3/+3 until end of turn.

Raging Redcap

Double strike (This creature deals both first-strike and regular combat damage.)

Buccaneer's Bravado

Choose one —
• Target creature gets +1/+1 and gains first strike until end of turn.
• Target Pirate gets +1/+1 and gains double strike until end of turn.

Uncaged Fury

Target creature gets +1/+1 and gains double strike until end of turn.

Swashbuckler Extraordinaire

When this creature enters, create a Treasure token. (It's an artifact with "{T}, Sacrifice this token: Add one mana of any color.")
Whenever you attack, you may sacrifice one or more Treasures. When you do, up to that many target creatures gain double strike until end of turn.

Forest

Unleash the Inferno

Unleash the Inferno deals 7 damage to target creature or planeswalker. When it deals excess damage this way, destroy target artifact or enchantment an opponent controls with mana value less than or equal to that amount of excess damage.

Swamp

Violent Ultimatum

Invigorating Surge

Put a +1/+1 counter on target creature you control, then double the number of +1/+1 counters on that creature.

Raking Claws

Target creature gains double strike until end of turn.
Cycling {2} ({2}, Discard this card: Draw a card.)

Sword of Hours

Whenever equipped creature attacks, put a +1/+1 counter on it.
Whenever equipped creature deals combat damage, roll a d12. If the result is greater than the damage dealt or the result is 12, double the number of +1/+1 counters on that creature.
Equip {2} ({2}: Attach to target creature you control. Equip only as a sorcery.)

Solidarity of Heroes

Strive — This spell costs {1}{G} more to cast for each target beyond the first.
Choose any number of target creatures. Double the number of +1/+1 counters on each of them.

Druidic Ritual

You may mill three cards. Then return up to one creature card and up to one land card from your graveyard to your hand. (To mill a card, put the top card of your library into your graveyard.)

Bristly Bill, Spine Sower

Landfall — Whenever a land you control enters, put a +1/+1 counter on target creature.
{3}{G}{G}: Double the number of +1/+1 counters on each creature you control.

Devoted Druid

{T}: Add {G}.
Put a -1/-1 counter on this creature: Untap this creature.

Leyline Axe

If this card is in your opening hand, you may begin the game with it on the battlefield.
Equipped creature gets +1/+1 and has double strike and trample.
Equip {3} ({3}: Attach to target creature you control. Equip only as a sorcery.)

Meria, Scholar of Antiquity

Tap an untapped nontoken artifact you control: Add {G}.
Tap two untapped nontoken artifacts you control: Exile the top card of your library. You may play it this turn.

Lathril, Blade of the Elves

Menace (This creature can't be blocked except by two or more creatures.)
Whenever Lathril deals combat damage to a player, create that many 1/1 green Elf Warrior creature tokens.
{T}, Tap ten untapped Elves you control: Each opponent loses 10 life and you gain 10 life.

Copperhorn Scout

Whenever this creature attacks, untap each other creature you control.

Savageborn Hydra

Double strike
This creature enters with X +1/+1 counters on it.
{1}{R/G}: Put a +1/+1 counter on this creature. Activate only as a sorcery.

Indoraptor, the Perfect Hybrid

Bloodthirst X (This creature enters with X +1/+1 counters on it, where X is the damage dealt to your opponents this turn.)
Menace
Enrage — Whenever Indoraptor is dealt damage, choose an opponent at random. Indoraptor deals damage equal to its power to that player unless they sacrifice a nontoken creature of their choice.

Fractal Harness

When this Equipment enters, create a 0/0 green and blue Fractal creature token. Put X +1/+1 counters on it and attach this Equipment to it.
Whenever equipped creature attacks, double the number of +1/+1 counters on it.
Equip {2}

Deathreap Ritual

Morbid — At the beginning of each end step, if a creature died this turn, you may draw a card.

Desperate Ritual

Add {R}{R}{R}.
Splice onto Arcane {1}{R} (As you cast an Arcane spell, you may reveal this card from your hand and pay its splice cost. If you do, add this card's effects to that spell.)

Quick Draw

Target creature you control gets +1/+1 and gains first strike until end of turn. Creatures target opponent controls lose first strike and double strike until end of turn.