Can Convergent Mutation be played targeting a single friendly unit (e.g., Mundo) when there are no other friendly units available?

Ruling: No, Convergent Mutation cannot be played if there is only one friendly unit available. All spells and abilities require legal targets in order to be played.

Sequence:

• The spell requires two distinct friendly unit targets to be played
• Target 1: The first friendly unit whose might increases
• Target 2: The second friendly unit (must be "another" friendly unit), whose might is used to determine the size of the increase
• Without both valid targets, the spell cannot be played

Nuances:

• The same unit cannot be selected twice because the spell specifies "another" friendly unit
• This applies even if the player wants to play the card solely for other benefits (such as adding might to the trash)