Rise of the Hobgoblins — ruling 1

When the "enters" ability resolves, you choose the value of X, pay for it, and put the tokens onto the battlefield. You can activate mana abilities to pay for {X}, but no one can cast spells or activate abilities in response to this choice.

Rise of the Hobgoblins : règles, fonctionnement et interactions (MTG)

Rise of the Hobgoblins 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 this enchantment enters, you may pay . If you do, create X 1/1 red and white Goblin Soldier creature tokens. : Red creatures and white creatures you control gain first strike until end of turn.

How it works : Rise of the Hobgoblins

Original English text — Wizards of the Coast / Scryfall

#1August 1, 2008· Wizards of the Coast
When the "enters" ability resolves, you choose the value of X, pay for it, and put the tokens onto the battlefield. You can activate mana abilities to pay for , but no one can cast spells or activate abilities in response to this choice.
No other card is named in this ruling.