Perfect for clerics that want to push a wizard's teeth in! 😉

Does this work against breath attacks?

A dragon's breath weapon doesn't count as a magic spell or effect. It's considered an ability or 'breath weapon'. So unfortunately not, afaik.

Where can I find the actual card for this? 

Just get the shield master feat and use your reaction to fully negate a dragon’s breath.

Does this give you advantage on saves that must be rolled each turn? Such as fear effects etc?

"you have advantage on saving throws against spells and other magical effects" 

i would say on each spell or magical effect. 

fear is not necessarily a magical effect. some fear is intimidation or ability based. for example a dragon roaring isnt magical but can cause fear to those weak willed within earshot. but a ghost gripping your head to create a fear effect would be magical and thus you would have advantage. it also specifies  saving throws so if the fear doesnt have a save attached to it then this would not stop that fear regardless. 

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That's actually kinda cool.