Dooms and portents in play

Grim portents and impending dooms are your plans. They're what will happen unless the PCs intervene.

One of your basic GM moves is advance towards impending doom. Look at the grim portents for one of your threats, check the next one off, and show the PCs some sign that it's occurred or occurring. You might make this move when…

… the Seasons Change, and their roll results in a threat getting worse or threats abounding. In the next session, or during an upcoming scene, show them that a grim portent or doom has come to pass.
… the players roll a 6- and this is the hard move you want to make. You'll often do this for moves made during loose play, but not always.
… the PCs have spent time away from the area where a threat is active, and then they return to that area. Show them how things have gotten worse.

The first grim portent for Sajra is obvious to me: more children go missing! But I'm not quite sure what comes next. What are steps between "having crinwin collect children" and "Sajra subjugates Stonetop?"

Working backwards: what would happen just before the town being subjugated?

Looking at the GM moves for villains, I see demand concessions, obedience, or respect and think: it would give the town an ultimatum! Accept it as their master, their god even, or be destroyed. This lines up with its instinct (to indulge its ego). It can turn the weakwilled into fawning servants (one of its monster moves) but it wants the bulk of the town to recognize its beauty and magnificence and serve willingly. Okay, what would it do before making such an ultimatum? It would gain followers or allies in town. How would it do that? Possibly by finding someone's weakness and then making an offer, with strings attached. But how? Villains usually act through minions or intermediaries... the children! It will send some of the stolen children home, thoroughly under its influence, and have them spy and recruit followers.

That gives me the following grim portents and impending doom:

O More children go missing
O Some of the (entranced) children return
O Children recruit followers
O Reveals itself, demands servitude
O IMPENDING DOOM: Subjugates the town, killing or mesmerizing any opposition