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Lavalanche deals X damage to target player or planeswalker and each creature that player or that planeswalker's controller controls.
Because Lavalanche doesn't target any creatures, it will deal damage to creatures with shroud. Any damage it would deal to creatures with appropriate protection abilities will still be prevented, however.
If the targeted player has become an illegal target by the time Lavalanche resolves, Lavalanche doesn't resolve. Nothing will be dealt damage.
