Rule 437.3

When damage is dealt this way, reduce the Prevent Value being tracked on the Unit affected by the Prevent action by the prevented amount.

• 437.3.a If the Prevent Value is 0 or less, then Prevent is no longer being tracked on the Unit in question, and the effect…
• 437.3.b The reduced value is the newly tracked Prevent Value.
• 437.3.c If the Prevent Value is “All” then it remains “All.”

Official Core Rules