For Gandalf specifically, it helps that he was a powerful wizard, which opens up itself to lots of fun card designs, and that his character evolves significantly throughout The Lord of the Rings
In white, this most clearly manifests in the relatively new design space of group draw instants and sorceries
Card Set(s) -500 YEARS IN THE FUTURE- [OP-07] CARD VIEW OP07-101 | UC | CHARACTER Shaka Attribute Wisdom Block icon 2 Effect [Blocker] (After your opponent declares an attack, you may rest this card to make it the new target of the attack.) Trigger [Trigger] If your Leader is [Vegapunk], play this card
I should add that although I covered the rules set by Wizards, you should absolutely go and double check it yourself and see if there are updates before you print their proxies
(2018-04-27) If a white instant or sorcery spell you don't control causes you to gain life, Firesong and Sunspeaker's last ability triggers
It's a separate timeline of excellence that runs parallel to the main sets