Law takes the chain in hand and focuses his imago. In his mind's eye he can see the chain decaying, rusting away to powder in his hands... all he has to do is make it real. But he sees something else in his mind's eye: A ravenous emptiness staring back at him. He's seen it before - the black sea between him and Stygia, the land of the watchtower of the Moros. It's a gulf that surrounds the physical world and it stirs at his attempt to modify reality.
The others can feel the pulse of his spell, but it's different than all the other times. They can feel reality rippling around them, attempting to compensate for Law's magic, to reject the spell. All four mages know at once what they're experiencing, even if they've never felt it before: It's Paradox, moving through the waters of reality like a shark, displacing the surface as it hones in on the use of vulgar magic. It hasn't manifested, but it might. That's up to Law.
A member of the group is attempting to use vulgar magic for the first time and must check for Paradox (Heads-up: There's a house rule pertaining to Paradox Backlash damage, described in the first post of the OOC thread - it doesn't change how the likelihood or strength of a Paradox are determined, however, nor how a mage goes about mitigating one with mana).
Law has a Gnosis of 1 and thus has a base Paradox dice pool of 1. He's not using a rote nor a magical tool and there aren't any sleeper witnesses, so the pool remains unmodified. Law can choose to spend one point of mana to reduce the dice pool by 1. In this case the dice pool would be reduced to exactly 0 and a chance roll (10% chance of failure, rather than 30%) made. If a Paradox pool is ever reduced to less than 0, there is no chance of Paradox.
Rubberneck: Will Law spend a point of Mana?