She can… but if she doesn’t necessarily have time to dig one out or if it’s not in her hands at the moment, it’s simply a complex pattern between her fingers, as I said a cat’s cradle, but more complex. But as most creatures rely on sight to attack, it doesn’t matter if it takes her a moment or two longer to create the pattern, as unless she’s dead in those few breaths, it doesn’t matter, she can show the monster the pattern. Some don’t rely on sight (like the entangle or black tentacles spell. Basically the higher the dex check, the faster she is able to make the pattern.

Hmm, OK , so we assume she carries a portable loom to do it?

I guess there must be some kind of check involved as well.

Actually… not as much as you might think. The reason why *dexterity* is involved (part 1 of this article) is that she can do something like a “cat’s cradle” with her hands in order to cast some of her spells, shoving the pattern in front of the enemy’s eyes. If it can be done fast enough, the enemy suffers the effects.

Only problem I see is that the said character (the Weaver?) must spend serious downtime in order to prepare her spells. Plus, she is reliant of crafting rules (if any).