Combat Reflexes is tempting, and fits with their combat approach of wildly slashing at everything within reach of their battle dance.
4 pounds weight, same as a Longsword?
I'm thinking they can't speak, but might be persuaded to accept a peculiar dialect of Terran. Although if they live in families they might be able to communicate with each other. Perhaps they have a gestural/somatic language and speak by "dancing".
Rereading the language and tactics the wording looks clumsy:
Xavers have a gestural language through which they speak by "dancing".
Xavers can lie motionless as other creatures approach, looking like an inert weapon, then attack when characters carrying lots of metal come near. They cut with their razor sharp edges, swinging their bodies in a series of wild, circular slashes called a battle dance.
Xavers cannot speak, but have a gestural language, they "talk" to one another by dancing.
A xaver will lie motionless, looking like an inert weapon, then attacks when creatures carrying metal come near. They cut with their razor sharp edges, swinging their bodies in a series of wild, circular slashes called a battle dance.