A fairly straightforward card, perhaps why poor Shadowfax has never been reviewed. Neutral Unexpected Courage but for only one specific character, everyone's favorite wizard. It costs an extra resource but as a neutral that's not a problem, especially since it also grants ranged and sentinel. And it's likely worth it even in true solo where you can't use those traits.
Clearly designed for Hero Gandalf, but probably even better with OverHill UnderHill Gandalf, who would get to use all three of his 4-point stats. Readying is obviously only as good as the stats you get to use again, and it doesn't get better than that.
Important to note that it's not restricted, which is counterintuitive since most of the mounts in the game are. Not overly necessary since there aren't a lot of restricted attachments that can go on Gandalf, but good to remember.
It can be fetched by Westfold Horse-breeder, which lets you save some deck space by not needing to include too many copies of this card.
Flame of Anor is made even better by letting you turn that 4-7 into a ranged attack.