I have a question, when you cascade and you exile a card that has no legal targets what happens? For example you play enlisted wurm and you cascade a wear // tear and there are no artifacts or enchantments, what happens?
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You can't cast a spell if the required number of legal targets can't be chosen for it (C.R. 601.2, 601.2c). If you can't cast a card due to cascade (including if you can cast neither half of that card in the case of a split card like Wear & Tear [C.R. 708.3, 708.3a]), you simply don't and you "put all cards exiled [due to the resolving cascade ability] that weren't cast", including that card, "on the bottom of your library in a random order" (C.R. 702.84a, 101.3, 608.2d). See also this thread.
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