Bio: Meltron was the guardian of the gateway between Brimo's reality and true reality. He was not a corporeal being, but a part of the illusion created by Brimo. Though fearsome, he was a reflection of Brimo's specific will.
When he first encountered the Fourth Doctor and Sharon, for example, she was just waking from a night's sleep. Thus his inclination was less to battle, and more towards a nice cup of morning tea.