Wei Wuxian knows that the wolf isn't even real - he can see the shimmering outline that tells him it's just a figment of his overactive imagination - but he's still rooted to the spot, unable to move; he can't even lift his flute to his mouth (not that it would help at all against an imaginary wolf, but it would give him a measure of comfort).

Ironically, it's Fairy who saves him when she barrels through the illusion in her excitement to see him, shattering it completely.

As he falls to his knees, Fairy takes it as permission to come bounding over to him, pushing her furry head into his hand; it takes him a moment to realise that he's petting her, but when he does, he leaps up screaming and runs away, reminding Fairy (and everyone else around) that he's still not quite over his phobia yet... although there may yet be hope for him.