Sure
Targets are chosen when a spell or skill goes on the stack. Magda’s skill goes on the stack as quickly because it’s triggered, i.e. when the goal of Lightning Bolt is chosen upon casting. Her skill is triggered and on the stack even earlier than the focused creature can change into hexproof. The creature turning into hexproof won’t take away Magda’s skill from the stack, nor forestall the focusing on which already occurred. It simply turns the focused creature into an invalid goal.
115.1. Some spells and talents require their controller to decide on a number of targets for them. The targets are object(s) and/or
participant(s) the spell or skill will have an effect on. These targets are declared
as a part of the method of placing the spell or skill on the stack.
The targets can’t be modified besides by one other spell or skill that
explicitly says it will probably accomplish that.
The stack and determination will look one thing like one of many beneath – issues can resolve in barely completely different orders, however the final result is principally the identical barring different results:
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Lightning Bolt is forged and goes on the stack. Magda’s skill triggers and goes on the stack. Hexproof spell/skill is placed on the stack. Hexproof resolves. Magda’s skill resolves and creates a treasure. Lightning Bolt fails to resolve with an invalid goal.
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Lightning Bolt is forged and goes on the stack. Magda’s skill triggers and goes on the stack. Magda’s skill resolves and creates a treasure. Hexproof spell/skill is placed on the stack. Hexproof resolves. Lightning Bolt fails to resolve with an invalid goal.
