Pure mortals making magical circles

[Pyromancer]

In the books, even pure mortals can make magical circles, that, for example, protect them from ghosts or undead. How is this handled in the game?

[luminos]

I'd probably do it with a single roll of conviction, as long as the mortal in question knows how to make the circle.  If something that circles block wants to get in, I'd compare its conviction to the one rolled by a mortal.  If it was a named NPC, I'd let it roll conviction to try to force its way into the circle.  I'd let any mortal undo the circle with either a supplemental action or an action with difficulty of +0, depending on circumstances.

[wyvern]

I'd tend to do it as a maneuver (probably based off of lore, but conviction could work too) to set up an aspect.
And then, if something that doesn't have free will at all tried to cross the circle, I would (as the GM) compel that aspect against them - disallowing them from passing, but giving them (or their master, if appropriate) a fate point.  This could also apply to a mortal mage trying to use magic across a circle boundary (if they were in some way prevented from simply breaking the circle directly.)
For things with, well, let's call it "partial" free will (such as powerful fey), they'd have to spend an action trying to break the circle first (their conviction vs. whatever skill was used to set up the circle).
And for a pure mortal?  That aspect just doesn't apply; they can probably break it with a supplemental action, or otherwise go about their business without caring that you're in a circle.

This is the thing with aspects: they're only as powerful as the GM and players make them be.  In a game I'm running, one of the PCs conjured up a fog to foil a gunman; by base game mechanics, that just gives them one free tag on the "fog" scene aspect; a plus two bonus on one defense roll.  Not very satisfying.  So I compelled the aspect against the gunman (preventing him from even rolling to attack, but giving him a fate point)... and then turned around and compelled the aspect against the PCs, too.  Made the spell feel a lot more powerful.  This is the same sort of approach I'd use with a circle.

[MijRai]

Know how to do it, a Conviction roll, and a single physical stress (you need blood to seal it, unless trained).

[Chlorofiend]

Know how to do it, a Conviction roll, and a single physical stress (you need blood to seal it, unless trained).

True, it takes blood, but unless a character is really bleeding himself out, I don't really see it taking so much blood as to result in physical stress.

[babel2uk]

True, it takes blood, but unless a character is really bleeding himself out, I don't really see it taking so much blood as to result in physical stress.

Remembering that Stress isn't actually damage, what you're advocating is for a mortal with no magical ability to be able to do something that a Wizard can do using magic with no cost attached whatsoever. I think a point of stress (mental or physical) is an extremely cheap price to pay for what amounts to a 100% block against ghosts and undead, which lasts until the circle is broken. I'd actually be inclined to say that level of protection should be bought with a mild consequence -though I'd allow it to be mental or physical.

[sinker]

I think I'd likely give the mortal a penalty to the block. A pure mortal using only their blood for power is not going to create a very powerful threshold. Though I might not if they were willing to take some stress or consequences for it.