Greldo

Greldo is a goblin and the servant of a witch in service of the Kinshra. He looks to be wielding a steel spear and a wooden square shield, as well as wearing what looks like a bronze cap on his head. He also seems to wear a type of black goblin mail.

During the Black Knights' Fortress quest, he is assigned to obtain a certain type of cabbage from Draynor Manor for the invincibility potion, but the player foils their plan by dropping a regular cabbage in the cauldron.

He is in the room with the witch and the Black Knight Captain, which is sealed off, despite having a door.

If you listen to the grill in the Black Knight's Fortress, Greldo says "Yeth, Mithtreth" which could possibly mean that this goblin has a long tongue, or that he has trouble pronouncing an "s" and was saying "Yes, Mistress".

Trivia

 * Greldo appears to be the only modern day goblin in RuneScape whose name does not consist of an unpleasant word and a body part, e.g. Wormbrain, Grubfoot, General Bentnoze and General Wartface.