Il testo del draghetto parla di "exchange control".
Se in risoluzione viene a mancare una delle due parti che si scambiano, nessuno scambio viene effettuato.
Comprehensive Rules ha scritto:
Exchange
A spell or ability may instruct two players to exchange something (for example, life totals or control of two
permanents) as part of its resolution. When such a spell or ability resolves, if it can’t exchange the chosen
things, it has no effect on them.
Example: If a spell attempts to exchange control of two target creatures but one of those creatures is
destroyed before the spell resolves, the spell does nothing to the other creature. Or if a spell attempts
to exchange control of two target creatures but both of those creatures are controlled by the same
player, the spell does nothing to the two creatures.
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