Lingua franca
The summoning, to my amusement, isn't a mystic ritual or even close to it. We simply gather in a room that holds nothing too precious and is spacious enough.
Then I and Leaf stand on one edge of the room, while Zeke goes to another and hits one of the brass pipes with a tentacle hard enough to leave a dent.
For a minute, nothing happens. A tense silence, interrupted only by the ever-present heartbeat of the castle's machine heart, settles on the room.
"Maybe one dent isn't enough? Hit something else, Zeke!" I advise.
Zeke complies. Then he takes several steps back and watches.
I and Leaf watch, too. The sight of a ghost appearing out of thin air is exactly everything I expected it to be.
There's nothing at first but a sensation of an otherworldly presence. Then magic becomes visible lines in the air, as if an invisible artist draws a sketch of a person. Finally, the silhouette gains volume and color, if not opacity.