Alicornutopia

Does Fairyland have magical places like... dunno, caves with singing rocks or rivers that glow or whatever?

Sure!

If a nymph went to Fairyland and ate a fairy's food, how would they tell them their name? Or does fairy general-speak cover that too?

Do you mean a MUniverse nymoh (like Celo)? That is an interesting question. From the litlle I remember of MU canon, they can say their names magically even without being mindread, but that doesn't cover the fairy remembering the name or whether it properly counts.

If you mean a different type of nymoh, then I'll ask about the MU kind.

Now I'm wondering about an Isateian in Fairyland.

Nymphs can say their names. The fairy wouldn't be able to transfer the nymph directly, they'd have to make the nymph tell the second master their name (or make the nymph take food), but being able to say a name (let alone actually saying it) isn't required. Fairies have an easier time remembering names than many/most humans do.

I haven't decided whether or to what extent plain speaking covers sign language, but seeing a namesign would still count just fine for envassalization, it just might be complicated to deliver orders.

Why didn't Fulfilled!Promise Vassalize the Queen? She could have done it by hand-feeding her something.

She could have ordered her to "Order everyone you meet: "Order all your current and future Vassals a copy of this order and no other forevermore." Do not give any other Orders to anyone." together with the usual do not tell anyone your name, ect.

By the way that one was awesome. I read it three times and the

"No," beams Promise, and she takes off and breaks a branch off her tree and flies and flies and flies.

part maybe ten times.

I will probably go back and edit that one to, like, work, instead of just contain the highly emotionally satisfying word "no", at some point when I know how I want it. Your idea doesn't work because the queen can no longer be a master.

How does Blossom setting the Lord Ruler on fire work with hin being her master? Were the dart vials sufficiently foodlike, or did the vassal him using some other principle?

The dart vials vassalized Alendi to Thorn, not Blossom (he owns the sugar in the sugar water). Blossom had a contingency to set attackers on fire which didn't require her willful intervention.