Bruni's laser-generating form keeps out competing monsters and angry mobs. Grani's horseform can cross the firewall, presumably carrying one or at most two people with her; she creates a sort of intake for new servants. Rinkrank gives her the burned cloak scrap and sets her loose, hoping she'll lead a small group back to the mountain as she tries to free her sisters.
Anyways, that's my take. It's a humble 1pager, so -- you know -- sometimes scant on details.