By Force

Comet Storm

Multikicker {1} (You may pay an additional {1} any number of times as you cast this spell.)
Choose any target, then choose another target for each time this spell was kicked. Comet Storm deals X damage to each of them.

Sami, Wildcat Captain

Double strike, vigilance
Spells you cast have affinity for artifacts. (They cost {1} less to cast for each artifact you control.)

Duelist's Flame

Until end of turn, target blocked creature you control gets +X/+0 and gains trample and "Whenever this creature deals combat damage to a player, look at that many cards from the top of your library. Exile up to one nonland card from among them and put the rest on the bottom of your library in a random order. You may cast the exiled card without paying its mana cost."

Commune with Lava

Exile the top X cards of your library. Until the end of your next turn, you may play those cards.

Martial Coup

Create X 1/1 white Soldier creature tokens. If X is 5 or more, destroy all other creatures.

Ysgard's Call

Create X 1/1 white Soldier creature tokens. (Then exile this card. You may cast the artifact later from exile.)

Horn of Valhalla

Equipped creature gets +1/+1 for each creature you control.
Equip {3}

Horn of Valhalla // Ysgard's Call

Balduvian Rage

Target attacking creature gets +X/+0 until end of turn.
Draw a card at the beginning of the next turn's upkeep.

Electrodominance

Electrodominance deals X damage to any target. You may cast a spell with mana value X or less from your hand without paying its mana cost.

Divine Deflection

Prevent the next X damage that would be dealt to you and/or permanents you control this turn. If damage is prevented this way, Divine Deflection deals that much damage to any target.

Decree of Justice

Create X 4/4 white Angel creature tokens with flying.
Cycling {2}{W} ({2}{W}, Discard this card: Draw a card.)
When you cycle this card, you may pay {X}. If you do, create X 1/1 white Soldier creature tokens.

Red Sun's Twilight

Destroy up to X target artifacts. If X is 5 or more, for each artifact destroyed this way, create a token that's a copy of it. Those tokens gain haste. Exile them at the beginning of the next end step.

Grand Crescendo

Create X 1/1 green and white Citizen creature tokens. Creatures you control gain indestructible until end of turn.

Forth Eorlingas!

Create X 2/2 red Human Knight creature tokens with trample and haste.
Whenever one or more creatures you control deal combat damage to one or more players this turn, you become the monarch.

Jacked Rabbit

Ravenous (This creature enters with X +1/+1 counters on it. If X is 5 or more, draw a card when it enters.)
Whenever this creature attacks, create a number of 1/1 white Rabbit creature tokens equal to this creature's power.

Aurelia's Fury

Aurelia's Fury deals X damage divided as you choose among any number of targets. Tap each creature dealt damage this way. Players dealt damage this way can't cast noncreature spells this turn.

Crackle with Power

Crackle with Power deals five times X damage to each of up to X targets.

Heliod's Intervention

Choose one —
• Destroy X target artifacts and/or enchantments.
• Target player gains twice X life.

Jaya's Immolating Inferno

(You may cast a legendary sorcery only if you control a legendary creature or planeswalker.)
Jaya's Immolating Inferno deals X damage to each of up to three targets.

Kozilek's Command

Choose two —
• Target player creates X 0/1 colorless Eldrazi Spawn creature tokens with "Sacrifice this token: Add {C}."
• Target player scries X, then draws a card.
• Exile target creature with mana value X or less.
• Exile up to X target cards from graveyards.

Entreat the Angels

Create X 4/4 white Angel creature tokens with flying.
Miracle {X}{W}{W} (You may cast this card for its miracle cost when you draw it if it's the first card you drew this turn.)

Captain's Maneuver

The next X damage that would be dealt to target creature, planeswalker, or player this turn is dealt to another target creature, planeswalker, or player instead.

March of the Canonized

When this enchantment enters, create X 1/1 white Vampire creature tokens with lifelink.
At the beginning of your upkeep, if your devotion to white and black is seven or greater, create a 4/3 white and black Vampire Demon creature token with flying.

March of Reckless Joy

As an additional cost to cast this spell, you may exile any number of red cards from your hand. This spell costs {2} less to cast for each card exiled this way.
Exile the top X cards of your library. You may play up to two of those cards until the end of your next turn.

Finale of Glory

Create X 2/2 white Soldier creature tokens with vigilance. If X is 10 or more, also create X 4/4 white Angel creature tokens with flying and vigilance.

Champions from Beyond

When this enchantment enters, create X 1/1 colorless Hero creature tokens.
Light Party — Whenever you attack with four or more creatures, scry 2, then draw a card.
Full Party — Whenever you attack with eight or more creatures, those creatures get +4/+4 until end of turn.

Meteor Blast

Meteor Blast deals 4 damage to each of X targets.

Eiganjo Uprising

Create X 2/2 white Samurai creature tokens with vigilance. They gain menace and haste until end of turn.
Each opponent creates X minus one 2/2 white Samurai creature tokens with vigilance.

Purphoros's Intervention

Choose one —
• Create an X/1 red Elemental creature token with trample and haste. Sacrifice it at the beginning of the next end step.
• Purphoros's Intervention deals twice X damage to target creature or planeswalker.

Release the Gremlins

Destroy X target artifacts. Create X 2/2 red Gremlin creature tokens.

March of Otherworldly Light

As an additional cost to cast this spell, you may exile any number of white cards from your hand. This spell costs {2} less to cast for each card exiled this way.
Exile target artifact, creature, or enchantment with mana value X or less.