The Reaper, King No More 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

When The Reaper enters, put a -1/-1 counter on each of up to two target creatures. Whenever a creature an opponent controls with a -1/-1 counter on it dies, you may put that card onto the battlefield under your control. Do this only once each turn.

Complete guide

The Reaper, King No More is a powerful Scarecrow that dominates the battlefield by weakening foes and bringing them back under your command. This legendary artifact creature turns your opponents' losses into your gains, provided you can mark them for death first. Understanding the timing of its triggered abilities is key to maximizing your spectral harvest.

Marking and Reaping

When The Reaper, King No More enters the battlefield, you choose up to two target creatures to receive -1/-1 counters. This immediately shrinks their stats and sets them up for the second ability. If a creature an opponent controls has a -1/-1 counter on it and dies, The Reaper allows you to return that card to the battlefield under your control. Note that the creature only needs to have a -1/-1 counter on it at the moment it dies; it doesn't matter how the counter got there or how the creature died.

The Resolution Process

Step one: The Reaper enters the battlefield and its first ability triggers. You choose targets and, upon resolution, place the counters. Step two: If a creature with such a counter dies, the second ability triggers. Step three: As the trigger resolves, you decide whether to use the effect. Because it says 'you may,' you can choose not to if you wish to save the 'once each turn' limit for a better target later.

Timing and Limits

A common mistake is forgetting the 'once each turn' restriction. This limit applies to the player, not the specific instance of the creature card; however, if The Reaper leaves the battlefield and returns, it is a new object and the limit resets. Additionally, the creature card must actually reach the graveyard for the ability to trigger. If an effect exiles the creature instead of letting it die, The Reaper cannot bring it back.

Strategic Deployment

Play The Reaper when you have a way to finish off a creature immediately or when your opponent has high-value utility creatures. Since it costs generic or colored mana, it fits easily into various decks. It is particularly effective during your opponent's turn if you have instant-speed removal, allowing you to bypass the 'once each turn' restriction by using it once on your turn and once on theirs.

Interaction examples

Draining the Life Out

Gray Merchant of Asphodel

If your opponent controls Gray Merchant of Asphodel, you can cast The Reaper and target the Merchant with a -1/-1 counter. If you then destroy the Merchant, The Reaper's ability triggers. The Merchant enters the battlefield under your control, triggering its own ability. This counts your devotion to black, including the {B} symbols in The Reaper's mana cost, potentially resulting in a massive life swing.

The Grim Cycle

Syr Konrad, the Grim

With Syr Konrad, the Grim on your board, every step of The Reaper's process becomes lethal. When an opponent's creature with a -1/-1 counter dies, Syr Konrad deals 1 damage. When The Reaper's ability resolves and you put that creature onto the battlefield under your control, it 'leaves the graveyard,' causing Syr Konrad to deal another 1 damage to each opponent.

Guide written with AI from the official text and rulings. Official English text prevails.