Caught in the Crossfire

Spree (Choose one or more additional costs.)
+ {1} — Caught in the Crossfire deals 2 damage to each outlaw creature. (Assassins, Mercenaries, Pirates, Rogues, and Warlocks are outlaws.)
+ {1} — Caught in the Crossfire deals 2 damage to each non-outlaw creature.

Great Train Heist

Spree (Choose one or more additional costs.)
+ {2}{R} — Untap all creatures you control. If it's your combat phase, there is an additional combat phase after this phase.
+ {2} — Creatures you control get +1/+0 and gain first strike until end of turn.
+ {R} — Choose target opponent. Whenever a creature you control deals combat damage to that player this turn, create a tapped Treasure token.

Three Steps Ahead

Spree (Choose one or more additional costs.)
+ {1}{U} — Counter target spell.
+ {3} — Create a token that's a copy of target artifact or creature you control.
+ {2} — Draw two cards, then discard a card.

Atarka's Command

Choose two —
• Your opponents can't gain life this turn.
• Atarka's Command deals 3 damage to each opponent.
• You may put a land card from your hand onto the battlefield.
• Creatures you control get +1/+1 and gain reach until end of turn.

Riku of Many Paths

Whenever you cast a modal spell, choose up to X, where X is the number of times you chose a mode for that spell —
• Exile the top card of your library. Until the end of your next turn, you may play it.
• Put a +1/+1 counter on Riku of Many Paths. It gains trample until end of turn.
• Create a 1/1 blue Bird creature token with flying.

Explosive Derailment

Spree (Choose one or more additional costs.)
+ {2} — Explosive Derailment deals 4 damage to target creature.
+ {2} — Destroy target artifact.

Shifting Grift

Spree (Choose one or more additional costs.)
+ {2} — Exchange control of two target creatures.
+ {1} — Exchange control of two target artifacts.
+ {1} — Exchange control of two target enchantments.

Artistic Refusal

Convoke (Your creatures can help cast this spell. Each creature you tap while casting this spell pays for {1} or one mana of that creature's color.)
Choose one or both —
• Counter target spell.
• Draw two cards, then discard a card.