I'd go with "Twilight of the Space Explorers", as it seems like a fitting title for an ending. Even if it doesn't have anything to do with vampires. Or any of the other things that get connected to that time of day. It's a pretty cool word, so I guess you'll just have to live with it also being quite popular.
(If this hadn't occurred to you, and the title is now tarnished or even ruined, sorry about that.)"All Sardy Things . . ." sounds a bit too crude for Indavo, and "Space Explorers in My Pants" sounds like something the Immortal Emperor would be the one saying/thinking/feeling as he'll be the one getting those space explorers in his pants. But it really doesn't come off as something he'd say or think, does it?