User blog comment:Argulor/Nightshade's vision---what does it mean?/@comment-1298206-20141025230846/@comment-26538658-20151117222320

If Swartt had taken the mountain, this silver badger may represent Death itself. I mean, Sixclaw has dodged it for so long, it'll finally catch him.

Another way to interpret it is to say that a "silver badger" is their way of saying "dark horse". No one would expect that beast to kill Swartt, but some unnamed beast unexpectedly kills him. Maybe it was a member of his horde.