Runy
Brogg, your choices to enter the library are through this metal hexagonal room, or back downstairs, past the fountain, and up again. The dumbwaiter (really a brass elevator) opens up into the back of the castle here on the Library level, where this demon guy is hanging out.
There's not really a pentagram, but there are a ton of little brownish runes along the perimeter of the floor, each about an inch across, separated by a quarter inch. For those of us reading beyond the States, each rune is 3 cm, separated by 1 cm. The runes are rather intricate. As you're studying them, the demon looks at the floor too. "
Impressive work for a fleshling," it says, shrugging. The demon yawns and crosses its four arms.