2021-02-05 : The value of X is based on the number of creatures the player controls of the chosen type as Pact of the Serpent resolves.

2021-02-05 : You choose the target player as you cast Pact of the Serpent, but you don't choose the creature type until the spell resolves.

2021-02-05 : You must choose an existing creature type, such as Squirrel or Knight. You can't choose card types (e.g., artifact) or supertypes (e.g., snow).