The form filter is a piece of Nekross technology which they could use to appear as other species, it could be worn as either a collar on the neck or a bracelet on the wrist and was activated with the touch of a button. As well as copying the form of a human and taking their place, a Nekross can also assume their own unique human identity.
Lexi used a form filter to assume a human disguise, "Lucy". Varg shortly after used a form filter to assume the form of Stephanie Gaunt. On both occasions the form filter was worn as a collar on the neck.
Varg used a form filter again, this time worn as a bracelet on the wrist, taking on the human identity, "Rick Towers".Lexi later used a wrist-worn form filter when she assumed her "Lucy" identity a second time.