A player may not make choices during this step that will deterministically result in illegal choices or actions later in this process unless they have no choice. Example: A player plays a card which reads “As an additional cost to play this, kill the unit you control with the most Might. Give a friendly unit +[M] equal to the killed unit’s Might this turn. Predict 2.” They cannot choose to target their unit with the highest Might during this step of finalization.
§ 355.16 Core Rules PDF (officieel)
§ 355 2. Make relevant choices.