Jonas

"This is gonna sound mad, but it looked like Jonas had a tail."

- Merlin to Gaius Jonas was an unknown species with a green, reptilian tail. He was the servant and accomplice of the Troll Lady Catrina who was ultimately killed by Arthur Pendragon.

Biography
Jonas accompanied Lady Catrina when she arrived in Camelot and was in fact an accomplice in her plan of becoming Queen. Jonas provided the troll Lady Catrina with potions. It appears that he also brewed the potions, indicating his proficiency with magic. Jonas served Catrina loyally and devotedly and often prepared treats for her. Despite his otherwise human appearance, it was when Merlin noticed Jonas had a reptilian tail that he began to become suspicious of Lady Catrina's presence in Camelot. When Lady Catrina revealed her true troll form and the enchantment placed upon Uther Pendragon was broken, a fight broke out and Jonas was eventually killed by Arthur, who stabbed him (Beauty and the Beast).

Abilities
Jonas possessed a great aptitude for Troll magic as he was able to create potions that transformed the troll version of Catrina into a normal human woman, the real Lady Catrina, thus disguising her true form and allowing her to trick the court of Camelot.

Physically, Jonas was quite strong and he was able to easily lift Merlin over his head.