Spectacular Showdown

Put a double strike counter on target creature, then goad each creature that had a double strike counter put on it this way. (Until your next turn, those creatures attack each combat if able and attack a player other than you if able.)
Overload {4}{R}{R}{R} (You may cast this spell for its overload cost. If you do, change "target" in its text to "each.")

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

Chaos Terminator Lord

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

Forest

Heroic Intervention

Permanents you control gain hexproof and indestructible until end of turn.

Collective Resistance

Escalate {G} (Pay this cost for each mode chosen beyond the first.)
Choose one or more —
• Destroy target artifact.
• Destroy target enchantment.
• Target creature gains hexproof and indestructible until end of turn.

Sweeping Cleave

Target creature you control gains double strike until end of turn. (Then exile this card. You may cast the artifact later from exile.)

Two-Handed Axe

Whenever equipped creature attacks, double its power until end of turn.
Equip {1}{R}

Two-Handed Axe // Sweeping Cleave

Into the Wilds

At the beginning of your upkeep, look at the top card of your library. If it's a land card, you may put it onto the battlefield.

Horn of Greed

Whenever a player plays a land, that player draws a card.

Defend the Rider

Choose one —
• Target permanent you control gains hexproof and indestructible until end of turn.
• Create a 1/1 colorless Pilot creature token with "This token saddles Mounts and crews Vehicles as though its power were 2 greater."

Lizard Blades

Double strike
Equipped creature has double strike.
Reconfigure {2} ({2}: Attach to target creature you control; or unattach from a creature. Reconfigure only as a sorcery. While attached, this isn't a creature.)

Critical Hit

Target creature gains double strike until end of turn.
When you roll a natural 20, return this card from your graveyard to your hand. (A natural 20 is a roll that displays 20 on the die.)

Origin of Metalbending

Choose one —
• Destroy target artifact or enchantment.
• Put a +1/+1 counter on target creature you control. It gains indestructible until end of turn. (Damage and effects that say "destroy" don't destroy it.)

Kediss, Emberclaw Familiar

Whenever a commander you control deals combat damage to an opponent, it deals that much damage to each other opponent.
Partner (You can have two commanders if both have partner.)

Raking Claws

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

Blood Mist

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

Psychotic Fury

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

Fire Nation Palace

This land enters tapped unless you control a basic land.
{T}: Add {R}.
{1}{R}, {T}: Target creature you control gains firebending 4 until end of turn. (Whenever it attacks, add {R}{R}{R}{R}. This mana lasts until end of combat.)

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.

Tamiyo's Safekeeping

Target permanent you control gains hexproof and indestructible until end of turn. You gain 2 life. (A permanent with hexproof and indestructible can't be the target of spells or abilities your opponents control. Damage and effects that say "destroy" don't destroy it.)

Sangrite Surge

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

Loot, Exuberant Explorer

You may play an additional land on each of your turns.
{4}{G}{G}, {T}: Look at the top six cards of your library. You may reveal a creature card with mana value less than or equal to the number of lands you control from among them and put it onto the battlefield. Put the rest on the bottom in a random order.

Twice the Rage

Target creature gains double strike until end of turn. (Then exile this card. You may cast the creature later from exile.)

Two-Headed Hunter

Menace (This creature can't be blocked except by two or more creatures.)

Two-Headed Hunter // Twice the Rage

Twinferno

Choose one —
• When you cast your next instant or sorcery spell this turn, copy that spell. You may choose new targets for the copy.
• Target creature you control gains double strike until end of turn. (It deals both first-strike and regular combat damage.)

Mountain

Courser of Kruphix

Play with the top card of your library revealed.
You may play lands from the top of your library.
Landfall — Whenever a land you control enters, you gain 1 life.

Amarant Coral

Trample
Amarant Coral attacks each combat if able.
No Mercy — Whenever Amarant Coral deals combat damage to an opponent, it deals that much damage to each other opponent.

Explore

You may play an additional land this turn.
Draw a card.

Lightning Greaves

Equipped creature has haste and shroud. (It can't be the target of spells or abilities.)
Equip {0}

Seifer Almasy

Whenever a creature you control attacks alone, it gains double strike until end of turn.
Fire Cross — Whenever Seifer Almasy deals combat damage to a player, you may cast target instant or sorcery card with mana value 3 or less from your graveyard without paying its mana cost. If that spell would be put into your graveyard, exile it instead.

Steely Resolve

As this enchantment enters, choose a creature type.
Creatures of the chosen type have shroud. (They can't be the targets of spells or abilities.)

Fanatic of Rhonas

{T}: Add {G}.
Ferocious — {T}: Add {G}{G}{G}{G}. Activate only if you control a creature with power 4 or greater.
Eternalize {2}{G}{G} ({2}{G}{G}, Exile this card from your graveyard: Create a token that's a copy of it, except it's a 4/4 black Zombie Snake Druid with no mana cost. Eternalize only as a sorcery.)

Dangerous

All creatures able to block target creature this turn do so.
Fuse (You may cast one or both halves of this card from your hand.)

Armed

Target creature gets +1/+1 and gains double strike until end of turn.
Fuse (You may cast one or both halves of this card from your hand.)

Armed // Dangerous

Oracle of Mul Daya

You may play an additional land on each of your turns.
Play with the top card of your library revealed.
You may play lands from the top of your library.

Uncaged Fury

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

Plaza of Heroes

{T}: Add {C}.
{T}: Add one mana of any color. Spend this mana only to cast a legendary spell.
{T}: Add one mana of any color among legendary permanents you control.
{3}, {T}, Exile this land: Target legendary creature gains hexproof and indestructible until end of turn.