Threaten is one of those cards players keep asking about. Here is, in plain words, what its official text says, the rulings published by Wizards of the Coast, and the combos players actually run.

Official card text

Untap target creature and gain control of it until end of turn. That creature gains haste until end of turn. (It can attack and this turn.)

How it works : Threaten

Original English text — Wizards of the Coast / Scryfall

No additional ruling has been published for this card.

Popular combos

Real combos played by the community, sorted by popularity.

#1
Alena, Kessig Trapper + Threaten + Reiterate
Gain control of all creatures until end of turnInfinite magecraft triggersInfinite mana creatures you control can produceInfinite red mana
1Cast Threaten by paying , targeting Alena.
2Holding priority, activate Alena by tapping it, adding at least seven .
3Cast Reiterate with buyback by paying , creating a copy of Threaten targeting Alena and returning Reiterate to your hand.
4Resolve the Threaten copy, untapping Alena and giving it haste until end of turn.
5Repeat from step 2.
6Once you have a large amount of , you may target opponent' creatures with the Threaten copies to take control of them.

Interactions with other cards

These cards' text mentions Threaten.

You've Been Caught Stealing

Choose one — • Threaten the Merchant — Each creature blocks this turn if able. • Bribe the Guards — You create a Treasure token for each opponent who was dealt damage this turn. (It's an artifact with "{T}, Sacrifice this token: Add one mana of any color.")