Catrina's enchanted necklace is a necklace with a red jewel/stone in the middle and a dull, silver, metal circle sorrounding it. It was given to Uther Pendragon by Lady Catrina, who used it to make Uther fall in love with her by putting a love spell on it. The enchantment made Uther fall under the troll's control, making him see her beautiful and perfect even when her true form was revealed. Catrina had to put a few drops of her blood while chanting: " Ic nemne þá grædige, yfele, formolsnung. Cume lǽn and mé getryme! Nu meaht þú begalan. Nu meaht þú begalan".
The Great Dragon said that the King had to cry tears of true remorce to break the enchantment. Gaius realised that Uther had to see Arthur die in order to cry. He and Merlin created a potion that gave the appearance of death (some form of poison). The antidote Merlin had would reverse the potion's effect immediately. The plan all worked out in the end and Jonas and Catrina were soon killed. Uther later told Arthur that he regretted many things he had done while he was under the troll's influence, implying what followed after he had to kiss the troll, under the influence of the spell. What happened to the magical object after those events is unknown (Beauty and the Beast).