I have a question regarding bloodfire colossus's ability...Will his ability damage planeswalkers?
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Bloodfire Colossus's current wording is still "deals 6 damage to each creature and each player". Under current rules, this effect will not deal damage to planeswalkers.
In general, the Dominaria update didn't change any "each opponent" or "each player" in the text of spells or abilities (examples include Bloodfire Colossus, Atarka's Command, Earthquake, and Flame Rift; review C.R. 108.1; see also this thread and this thread). Moreover, with Dominaria, the planeswalker redirection effect in the rules was eliminated (C.R. 306.7 now says that this used to exist previously).
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