"I've heard of such worlds, but I've never seen one myself. I know only my own domain; I can't tell you how the magic will act elsewhere. But..." The voice hesitates. "The skull mask does help the bearer learn spirit magic faster and in more depth. And that might help you use it effectively in strange situations. I can't be sure, though."

He considers this. 

"The skull mask," he decides.

"Very well. The next choice is Eyes. The five customary options are Blind, Hollow, Mirrored, Eightfold, and Ethereal. Blind masks have no eyes but enhance your other senses to compensate for the lack of sight; Hollow eyes show your own eyes clearly and give you clear sight into the truth of things; Mirrored eyes let you see the intentions and nature of whoever gazes into them; Eightfold eyes see more colours, more clearly and precisely; and Ethereal eyes grant an effect similar to the soulsight spectacles, but more refined. There is a Complication that allows you to craft one eye in one style and the other in a different style, although it can be hard to get used to seeing two very different things at once."

"What else does the Complication do?"

"Only that. There is another one that allows mixing two Mouth options, and another that allows mixing two Runes, but we haven't gotten there yet."

"Are Complications not meant to be negative? That was the impression I had gleaned."

"They complicate things. Whether they are negative depends on perspective. For each Complication I offer, some people think it is obviously the worst one and they would rather not have a mask at all than take it, while some think it is obviously a good thing that they want to have."

"I see. If one combines selects Blind as one of the two options, wouldn't it not have the seeing-two-things downside?"

"It would not, but it would instead have the downside of making it much harder to see distances the way a pair of eyes normally does. And the enhancement to your other senses would be a little less powerful."

"I see. I'll take the complication and craft one eye Hollow and the other Ethereal."

"Very well. Here."

There is an odd sensation, like alien muscle memory, like his hands just know which tools to pick up and how to use them. He doesn't need to follow the provided directions if he doesn't feel like it, but it's as easy—and as easy to accidentally slip into without meaning to—as absently fiddling while thinking about something else.

And, if he lets the Assistant's directions lead him, the eyes of the mask begin taking shape under his hands. One empty socket carved of soulstuff, and one with a gleam of silvery light in its black depths.

"Next is the Nose, which can be Smooth, Human, Strange, Slit, or Snout. Smooth means no nose, and no need or ability to breathe. Human means a humanlike nose, which makes breathing more calming and invigorating, so that no matter how tired or upset you are, a few deep breaths will always help you steady yourself a little longer. Strange means a nose that resembles none of the usual types of noses, and carries a magical effect that makes you almost impossible to recognize as the same person with the mask on versus off. Slit means a simple opening such as the nose hole in a skull, and gives you the power to exhale clouds of toxic gas to which you are immune. Snout means the nose of a beast, and gives you a fantastically powerful sense of smell and a perfect memory for scents."

"Human," he says, firmly and immediately. He's plenty good at keeping calm already, but no matter how tired or upset you are--that could be very useful for his own magic. 

"As you wish."

Somehow, as he continues shaping the mask, the human nose manages to work well with the skull aesthetic.

"The Mouth, then, can be Mouthless, Slot, Mandibles, Human, or Fangs. Mouthless removes the need and ability to eat, drink, and speak, and lets you communicate mind to mind with anyone nearby; Slot ensures that when you speak, you are heard by all and only those you mean to speak to, no matter how far away they are or who else is listening; Mandibles let you eat a mask to add one of its powers to your own; Human gives you the power to always know the right words to say what you mean to your audience, even if they're in a language you don't understand; and with Fangs you can bite someone to drain their lifeforce and restore your own."

"Does Mandibles have some downside that I don't understand? It seems like I could just make masks and then eat them."

"The added power is imperfect, not in balance with the rest of your mask; and weaker, most especially if the mask is unbonded when you eat it. And making a mask is a spiritually tiring endeavour, even once you learn how to do it, which could take many years. Those who take Mandibles most often intend to hunt other mask-bearers and eat their masks for power. You are correct, though, that you could do that and it would work. It would even help you learn mask-making more quickly, if you ate your scratch-work and prototypes."

"Mandibles, then." 

The Mandibles take shape in his guided hands. The mask is starting to get pretty clearly defined.

"Next, the five Runes: Fire, Air, Water, Earth, and Spirit. Each has a passive effect, protecting you from the element and supporting you with it, and an active effect, allowing you to learn how to shape and control it. If you take the Complication to combine two Runes, you may take only one effect from each."

"What are the active and passive effect for each rune?"

"Fire's passive effect makes you immune to burning, Air to falling, Water to drowning. Earth grants immense durability. Spirit makes you age half as fast and heal twice as quickly, as a side effect of strengthening your spirit. The active effects grant you a talent for the relevant form of elemental magic, which you then have to learn how to use."

"What does elemental spirit magic look like?"

"It's the same magic that lets you see and manipulate soulstuff, or create the tools to see and manipulate soulstuff. It's by far the hardest elemental magic to learn, but with your choices so far you should have a very good headstart indeed."

"What does immunity to falling look like?"

"No matter how far you fall, you will always land lightly enough not to hurt yourself."

"I'll complicate the rune with Earth passive and Spirit active."

"Very well then. Here..."

This is the most delicate operation yet; the mask, still half-formed, turns under his hands so that he can pick up an as-yet-unused tool and carefully engrave a complicated arrangement of lines and curves into the inner surface of its forehead. The Assistant stays quiet through the process, as though focusing wholly on the work.

Then: "Where were we... ah yes, Decorations. Horns, Feathers, Scales, Gems, Flowers, Engravings, Trinkets, Tendrils, Branches, or Shadows. Horns enhance strength and endurance; Feathers enhance speed and grace, and allow you to summon and dismiss a pair of wings. Scales make you impervious to mundane physical injury. Gems transform your body into its ideal shape. Flowers shed petals that can be used to make paper and textiles. Engravings enhance Runes. Trinkets can be expended to completely heal a person. Tendrils can be used as extra limbs. Branches make you heal a little bit faster and a lot more completely, so you never age or scar as long as you wear the mask often enough. Shadows let you become insubstantial at will."