Could you please explain why the sentence « Alors, reste avec nous et sois notre soeur. »* appears to be using the subjunctive form of être if there is no "que" before it. It makes sense that "stay with us" is in the imperative and "be our sister" is subjunctive in that it is a desire/hope/want. Is this just a special case or have I misunderstood the grammar?
*Quote from a traditional fairytale.