The official website for The Settlers of Catan

Question about Combination of “Traders & Barbarians” with “Cities & Knights” Catan Event Cards + C&K - How do I combine the Alchemist with the “Catan Event Cards”?

Answer

Instead of revealing an Event Card, play the Alchemist. Determine a production number. Determine the result shown by the red die. Only roll the event die.

If all participants in a game want to agree on a different procedure, they certainly are free to do so. If, in addition to the Alchemist, you would like to reveal an event card, we recommend that after playing the Alchemist you first determine the production number, then resolve the result of the event die roll, then draw an event card (of which only the event is resolved, provided that an event is described on it), and lastly distribute the resources. Please note that this is only a variant, not the official rule.