Underworld: Rise of the Lycans, Lucian's (Hero) Moon Collar

original movie costume

The moon collars were designed with silver spikes on the inside of the front of the collar, pricking and scratching the skin of the neck of the Lycan wearing the collar. This was done to prevent Lycans from undergoing “the change”, becoming their Werewolf form. Highly allergic to silver, the Lycans could not take on their bestial forms so long as the silver from the collars was embedded in their skin, making them less threatening to Vampires.

This particular collar was worn by Michael Sheen as 'Lucian'. It can open and close, aswell as having a hole for a key to unlock the collar which is a very nice little detail. 

https://www.instagram.com/lycanreaper/