Can you go over how Island Sanctuary and Sylvan Library interact? Can I “draw cards” and not pay life? Can I skip drawing and still lose life?
Island Sanctuary can replace any draw in your draw step, or multiple draws even, though there's no additional effect if you skip more than one draw in a single draw step.
When your draw step begins, you'll draw your usual card for the turn.Sylvan Library triggers after your normal draw and when that trigger resolves, you can choose to draw two cards. If you choose to draw, then you'll do the pay life or put cards back thing.
Assuming that you choose to draw with Sylvan Library and choose to skip one of the draws for Island Sanctuary, then you'll need to pay 4 life for each of the other two cards you've drawn this turn that you want to keep or put them back on your library. (If you replace two draws, then you have to pay life to keep your one drawn card.)
Sylvan Library cares about any card you've drawn this turn, not just the cards drawn with Sylvan Library, so there's no way to get a free Island Sanctuary shield with it.
