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Historical Rules · 1 June 2020

Rule 115.4

Official source text from the 1 June 2020 Rules release

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Some spells and abilities that refer to damage require “any target,” “another target,” “two targets,” or similar rather than “target [something].” These targets may be creatures, players, or planeswalkers. Other game objects, such as noncreature artifacts or spells, can’t be chosen.

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