Whiplash Trap

Mana cost: {3}{U}{U}
Type: Instant — Trap
Set: Zendikar #77 (common)
Price: $0.21 USD

If an opponent had two or more creatures enter the battlefield under their control this turn, you may pay {U} rather than pay this spell's mana cost.
Return two target creatures to their owners' hands.

Whiplash Trap has 5 printings, first in Zendikar (2009). EDHREC ranks it #16,112 among Commander cards. It appears most in Kalamax, the Stormsire decks (668 on EDHREC). 1 public deck on TCG runs it. It has 5 official rulings.

Legality

commander: legal
legacy: legal
vintage: legal
pauper: legal
modern: legal
pioneer: not legal
standard: not legal
brawl: not legal

Public decks that run Whiplash Trap

Arcane Maelstrom - Commander 2020, led by Kalamax, the Stormsire

Commanders that run Whiplash Trap most

Deck counts from EDHREC.

Often played with Whiplash Trap

Cards that show up in the same decks on EDHREC.

Rulings

2009-10-01: You must target two creatures as you cast Whiplash Trap. If you can't (because just one creature is on the battlefield, perhaps), you can't cast the spell.
2009-10-01: Effects that increase or reduce the cost to cast a Trap will apply to whichever cost you chose to pay.
2009-10-01: You can target any two creatures, not just ones that entered this turn.
2009-10-01: Casting a Trap by paying its alternative cost doesn't change its mana cost or mana value. The only difference is the cost you actually pay.
2009-10-01: You may ignore a Trap's alternative cost condition and simply cast it for its normal mana cost. This is true even if its alternative cost condition has been met.