Horn of PlentyHow it works & interactions with other cards

How the Trigger Works

Whenever any player casts a spell, Horn of Plenty triggers. As that trigger resolves, the player who cast the spell has the option to pay {1}. If they do, a delayed triggered ability is created. This delayed trigger will not resolve immediately; instead, it waits until the beginning of the next end step to put a card into that player's hand.

Timing and Mana

The decision to pay {1} happens when the Horn of Plenty trigger resolves, which is always before the spell that triggered it actually resolves. If the spell is countered, the player still had the opportunity to pay the {1} and will still draw the card at the next end step. Note that you cannot pay more than {1} to draw multiple cards for a single spell; it is a one-time choice per trigger.

The Next End Step

The 'next end step' refers to the very next time an end step begins, regardless of whose turn it is. If you cast an Instant on your opponent's turn and pay {1}, you will draw the card at the end of their turn. If you cast a spell during an end step, the 'next' end step won't occur until the following turn, meaning you will have to wait quite a while for your card.

Interaction examples

Fueling the Horn

Gilded Lotus

With Horn of Plenty on the battlefield, you tap Gilded Lotus to add three blue mana. You then cast a spell using two of that mana. The Horn triggers, and you use the final remaining blue mana from your pool to pay the {1}. Even though your mana came from a single source, you successfully set up a card draw for the end of the turn.

Double Draw Synergy

Vanquisher's Banner

If you have both artifacts out and cast a creature spell of the chosen type, two triggers go on the stack. Vanquisher's Banner will let you draw a card immediately upon resolution. Horn of Plenty will ask for {1}; if you pay it, you will draw a second card, but only when the end step begins. This allows for massive hand replenishment in tribal decks.