Do you have to declare both targets for Convergent Mutation when it enters the chain, or can you choose the second unit during resolution?

Ruling: You must choose both targets when casting Convergent Mutation. You cannot add a spell or ability into the chain without providing all choices, and both units comply with the target requirements.

Nuances:

• This same principle applies to other cards like Ride the Wind, where you must declare both the unit and its destination when finalizing the spell.