Imogen sees the dust, and tries to move the claymore away, but it's already committed to the swing, and can't avoid it all.  The edge of the small cloud cast forth by Nicoli brushes against the blade, dust caressing metal almost gently- though the consequences are anything but.  Like a miniature swarm of termites, the crimson specks eat their way into the sword, ruining its integrity with frightening swiftness.

The swords-mistress raises an eyebrow at this. The weapon was certainly a good one, but this is not the first time she has lost a sword in battle, and there is no time for grief, only for analysis.  That dust is no ordinary equipment, something specifically chosen to counter her fighting style.  Whoever this man is, he's well-equipped, and likely has other tricks up his sleeves.  His dust will not touch her weapons again, she'll make sure of that, but she'll need to watch his hands, and be ready for anything.

The dust does its work fast, and will eat through the claymore within a few seconds.  But, in a fight, a few seconds is a long time, and Imogen still has control of the sword.  Though the dust is already ruining the claymore's edge and its integrity, it had done little to change its direction or momentum, and she is able to swing it around quickly and easily.  Nicoli, meanwhile, was sent into a skid, difficult to control and requiring him to get back on his feet before he does anything much.  The initiative is Imogen's.

Obviously, she makes use of this.  While Nicoli rolls forwards, the claymore follows him, swinging around as it does so until it's oriented horizontally, edge facing him.  As soon as the man tries to come up on his feet, it accelerates, rushing forwards and downwards to slam itself into his lower back.  Though it has already lost its cutting edge to the dust, as well as much of its mass, it is still a heavy length of metal, carrying enough force to knock Nicoli down unless he somehow intercepts or avoids it.  

This simple stike, however, is only half of the threat.  As the ruined claymore attacks, the scimitar rushes in towards Nicoli, as if seeking to aid its dying comrade in its last assault.  Though it took a little focus to get into position, the larger sword's actual attack is hardly a complex maneuver, and requires no attention to direct once set in motion- which means Imogen is free to focus on controlling the smaller blade far more carefully.  Nicoli's left arm moves to throw something, and while in motion it's difficult for the limb to make a dodge- so the scimitar strikes there, slashing upward to cut at the hand on the end of that arm, seeking to rid Imogen's enemy of some of those troublesome, dexterous fingers. 

Opportunity, however, comes to a swift end as smoke begins to flood the air.  The scimitar, as soon as its slash is completed, flies slightly backwards and then straight upwards, climbing into the air to hover about twenty feet above the arena floor.