Destroyer

A huge demonic otherworld creature which thrived on death and destruction.

If kept in silver chains, it could do little, but when Morgaine brought it to Earth, she freed it, hoping to force her old enemy and her beloved, Arthur, into the open.

Despite the Doctor's protestations that Arthur was dead, Morgaine instructed the Destroyer to obliterate everything.

Brigadier Lethbridge-Stewart shot the Destroyer with silver bullets. All the unreleased destructive force was turned back inwards and the Destroyer was itself destroyed.