Tonight, Doctor Who’s latest season comes to an end, as the Doctor and Ruby prepare to battle an almighty foe from the Time Lord’s past. But it also means there’s one last chance to see the most constant of factors in what has been a very up-and-down season—one more appearance from guest actress Susan Twist, who’s been Doctor Who’s most literally named Easter egg in a very long time.

Last we saw the erstwhile actress, Twist was playing Susan Triad—the nebulous Tech mogul head of Triad Technologies—who was revealed to be a herald of none other than Sutekh, the God of Death, a classic Who villain not seen on-screen in 50 years. But Triad was only the latest in a long line. It’s been the meatiest of the roles, but Twist has appeared in every episode of Doctor Who since last year’s Christmas special, “The Church on Ruby Road” (and even appeared before that, in Who’s 60th anniversary specials), playing different characters unified across time and space by her mysterious visage.

What that’s actually meant yet? That remains to be seen, other than as a tease for Sutekh’s inevitable rise—“The Legend of Ruby Sunday” climaxes with Triad becoming a harbinger of Sutekh, transformed into a skeletal vessel for his ancient power. Whether “The Empire of Death” turns her into a mook, or there’s more to just why she kept manifesting in the Doctor and Ruby’s adventures, we’ll find out tonight. But before that, let’s celebrate the Twists along the way, with our definitive ranking.