Let's see if we are still in niche - Nutcracker/Melee Hurter. Nutcracker is fulfilled by Arcane Fire and Swarm attack. Melee Hurter is fulfilled by Swarm Attack and Distraction, but might use a bit more. Something that makes an opponent think twice about actually attacking it. Maybe the swarm form is a veritable maelstrom(!) of blades, needles and sharp disks that can coalesce into a shape made up of sharp animated stuff.
Opportunist and Precise Strike would likely only be available in coalesced form. In that form, it might have a natural rapier attack.
For arcane fire, it would be useful for the creature to have spell-like abilities. That way, we can use most of the text.

Rename the ability to needle strike, dealing piercing damage, subject to DR?
For some reason, the name Kestenjar just appeared in my mind - for the single creature?
For the famility of anti-inevitables - infallibles?
Of course, those'll get a poll.