If you control more than one legendary creature with the same name and the "legend rule" begins applying again (perhaps because Council of Reeds leaves the battlefield), you'll immediately have to comply with the rule and put all but one of those permanents into the graveyard
With that said, it is an instant speed non-conditional removal spell so how popular expensive creatures like Lyra Dawnbringer get, as well as how valuable instant speed is, will dictate how much play Murder will see
There are multiple cards in most sets that are white and gain life
Synchro: Banish 3 random face-down cards from your opponent's Extra Deck, face-up
Scarily, that token copy enters with loyalty counters equal to the power of the creature you sacrificed to the loyalty ability, letting you easily throw his ultimate ability off straight away We're not quite as likely to see casualty return on a Planeswalker as we are compleated, as it was a set mechanic for Streets of New Capenna
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