The Emperor is the "father" card; stability, teaching and protection are a few of its themes.

Dusk fits the role of father figure for the group decently well, I think; he's one of the most stable people I know, and it's very rare to truly catch him off-guard. He's also often able to do his part to help out anyone else who may be having trouble.
(he's not actually that grumpy usually! That's just what the card calls for)